Monthly Journal of the Institute of Metals and Metallurgical Abstracts, Vol. 2, Part 5

v ers 7 0 1 & 7 0 2 to be p n n te d in th e half-y early y o lu m e :

Journal o f the Institute o f Metals, 1935, V ol. L V II.

Vo1, 2* Part 5.

THE ADYERTISEMENTS

The A d vertisem ents published in the M onthly Journal are increasing both in interest and in n um bers, which m ay be taken as an indication that advertisers are com ing to realize the particular value to th em of the specialized circulation of the Institute’s publications.

Advertisers judge the interest displayed in their advertise- ments by the enąuiries received. M em bers are reąuested, therefore, w hen m aking enąuiries of firm s advertising in this publication, to m ention the M onthly Journal of the Institute of M etals. By so doing they w ill be of serja^ cJp^ s.

the Institute.

/ąj?

[ P O L IT E C H N IK ']

__________ \________________

l_

an d

M E T A L L U R G IC A L A B STR A CTS

MAY, 1935

'JTight] \Entered a t Stattoners’ Hal,l

ON-FĘRItOUS ALIOYS

are unecjuallea for

C O N S I S T E N T OU A LITY

and are produced in

NOTCHED BARS, INGOTS, ROLLING SLABS, W IR E BARS, STICKS and SHOT

to

ADMIRALTY, A.I.D., B.E.S.A. and all Standard

Specifications

P a rtic u la r attention is draurn to our

STANDARDIZED ALUM INIUM ALLOYS for

SAND-CASTINGS, GRAVITY and PRESSURE DIE-CASTINGS and SPECIAL HIGH-TENSILE ALLOYS for AIRCRAFT and ADMIRALTY W O R K

Pr i n t k d i n Gr b a t Br i t a i n b y R ,c h a r o Cl a y a n d So n s, Lt d. , Bo n g a y, Su k i-o l ic.

ft*

From our w ide ra n c e w e a re ab le to supply refracto ry m a t­

eriale o f high q u ality su ita b le fo r m ost in dustrial purposes.

In our vario u s w orks, w hich a r e m o d e rn in d e s ig n a n d equipm ent, c a re is tak en in every s ta g e o f m a n u fa c tu re to ensure th a t our p rod u cts a re m a in t a in e d a t a u n ifo r m ly

high stan d ard .

For fuller particulars, ask for our Pamphlet, No. 1.

SCOTLAND

ALUMINIUM PROGREft

w ith o u t

1 i n e rs

This is the cylinder for a Cross engine, which uses an aluminium c y l i n d e r w i t h o u t l i n e r , w i t h an aluminium piston. Highly successful results have been obtained under test

^BRITISH ALUMINIUM^

j U Offi«: AD£ LAIDE UOUSE.KING WILLIAM S! LONDON,E.C.4

TELEPHONŁ : MANSION HOUSE 5561 8074 ( 5 LIN ES)

^ TELEGRAMS: CRYOLITE , BILGATE , LONDON . . .

M A N C H E S T E R R DH O U S E : w ^ 29’ o t T n R d " N ‘W -'' B IR M IN G H A M 4 : Lawley St.

M A N C H E S T E R . Deansgate House, 274, Deansgate. LE E D S 3* 66 Kirkstall RH N E W C A S T L E - O N - T Y N E i : M ilburn House. G L A S G O W € 2 : 1 1 3 , W ^ t R e g e t St!

^ ---— --- jiM.5 .3 5.

A ii i

ROCKING ELECTRIC ARC FURNACE FO R M ELTIN G NON - FER.R.OUS

AND FER.R.OUS M ETALS

M O D E R A P / D L V U N I F O R M L Y a n d

E C O N O M I C A L L Y .

B I R M I N G H A M E L E C T R I C F U R N A C E S L I M I T E D

Bi r l e c Wo r k s. Ty b u r n r o a d. Er d i n g t o n. Bi r m i n g h a m

i v

W E also make Sheet and Strip in Brass, Copper, Bronze and Nickel Silver, etc., Extruded Rods and Sections, and also “ D U R A L U M IN ” of which we are

the sole makers.

Jam C S H o o lll fiCcmipany limited

A .RG YLE STR EET WORKS, BIRMINGHAM,7.

Te/ephone: E A S T 1221 (P .B .E .). Telegrams: “ Booth, Birm ingham .” , Cab/es: Lieb e r’s 5 letter. A .B .C . 6th Edition. Ben tley’s Second Phrase. W e ste rn Union.

PRINCIPLES OF PHASE DIAGRAMS

By J. S. Marsh

Physical Metallurgist and Associate Editor, “ A lloys o f Iron Research,”

193 pages, 9X 6, illuslrated, 1 8/- net.

A generalised treatm ent of the principles of phase theory and a discussion of the ternary diagram s for the use of students, chem ists, m etallurgists and any others confronted w ith a problem of heterogeneous eąuilibrium .

CONTENTS :

Foreword Preface Fundamentals

Fundamentals (continued)

Systems of O ne o r T w o Components

Systems of Th ree Com ponents (T e rn ­ ary Systems— I)

Systems of Three Com ponents (T e rn ­ ary Systems— II)

Conclusion lndex

McGRAW-HILL

Aldwych House

P U B L IS H IN G CO. LTD.

London, W.C.2

a n ew service

to m em bers

Members who find it inconvenient to bring to the General Meetings copies of the Monthly Journal containing the papers to be discussed, may now purchase one loose copy of each paper.

Orders, which must be for one whole year in advance, should be sent to the Secretary without delay. The service will commence with the Autumn Meeting, 1935, papers.

Annual charge 5s., post free.

v i

AND ITS A L LOY S

are constantly being applied with advantage to new uses in industry. This applies particularly to extruded sections which we are now producing in almost any shape and of which some examples are shown below.

We would welcome an opportunity of discussing the

new applications o f this metal to your problems.

P O L IS H E D and P L A T E D S H E E T M E T A L S

ZIN C , T IN PLA TES, N IC K EL

SILVER, BRASS, ETC.

Plated with CHROMIUM, NICKEL, BRASS, COPPER

Please send us your enguiries:

Sheets up to 84 by 18 in.

Strips 84 in. by any width. Any gauge.

W . E. MARTIN & CO. LTD.

H O C K LEY

T e le p h o n e : N o r th e r n 2961-2.

M A N U F A C T U R E R S

BIR M IN G H A M , 19

T e le g ra m s : B E E Z E D D , B 'H A M .

OXYGEN

Masterof Metals

T h e f i r s t O x y * a c e t y l e n e r o d to be a p p r o v e d b y L l o y d 's f o r u e l d i n g p a r / s o f p n m a r y s t r u c t u r a l i m p o r t a n c e i n s h t p b u i l d i n g .

‘ A ida ’ S.M . N o. 1 R ods for the o x y - acetylene w eld in g of Steel for all p u rp oses w here h igh ten sile stren g th is reąu ired

S U P P L IE D IN 36" L E N G T H S IN T H E F O L L O W IN G D IA M E T E R S : 1" 5 " 3 " 7 " 1"

8 , 32 , 16 . 32 , 4

THE BRIT ISH OXYGEN CO., LTD.,

> V ictoria S ta tio n H o u se, W e stm in s te r , S.W . 1

’ ‘ 4 1 B .O .C . O x y g e n a n d D . A . W o r k s =; i:

. ‘ i n G t. B n t a i n a n d N . I r e l a n d a n d 2 3 0

i n A u s t r a h a , S o u t h A f r i c a a n d I n d i a . .

i • 'v ! : - 7 . • - •;!; • ; o ; ; : : 7

v i i i

For the economical production of tubes with absolutely uniform wali thickness we supply

T U B E E X T R U S I O N

of vertical o r horizontal type, also the required power w a ter plants consisting of pressure pumps and accumulators, the latter of the electrically controlled, com- pressed-air loaded typ e w ith o u t any pistons or floats, for which the H Y D R A U L IK Co.

owns patents in all countries of the world.

PRESS ES

British Agents: Aabacas Engineering Co., Ltd., 10 Canning Place, Liverpool, I

ix

APERIODIC

& MSCRO- C H E M I C A L B A L A N C E S

Please w rite for N e w List show- ing Instruments of the most ad- vanced design.

British Made by

L. O ER T LIN G LTD.

65 HOLBORN VIA D U CT, LONDON, E.C.1 Founded in London 1849.

TAS/Or. 1 1 6

N EO PH O T “ j

Epi-Microscope & Camera

A N EW IN STRU M EN T, designed on new lines. Covers every phase of metallography at magnifications from 2 0 0 0 x to less than unity, with rapid interchange from normal or oblique brightfield i 11 u m i nat io n to dark field or polar- ized light. The stages, motions and illuminators are all specially designed with a view to the utmost simplicity of operation.

Write fot list “ Mikro 1 4 1 ” giuing fu li particulars.

Carl Zeiss

Ltd.

Mortimer House, 37-41 Mortimer St., W.1

Grams: ALLOYS. S L O UGti

FOUNDRY SERYICES, LTD.

LONG A C R E, N E C H E LLS , BIRM INGHAM , 7

x i

V I T R E O S I L M U F F L E S

T H E

T H ER M A L SY N D IC A T E l™

V IT R E O S IL W O R K S W A L L S E N D - O N - T Y N E

London D e p o t :

Therm al House, O ld Pye Street, S . W . I

V IT R E O S IL , pure fused silica, withstands heat up to II0 0 °C . and is unaffected over long p e r io d s . It is t h e r e f o r e eminently suitable for muffles used for all metallurgical pur- poses, heat treatment, labora- to ry testing, etc. C ircular muffles as illustrated are made up to 10 ft. in len gth; other shapes and sizes are obtainable.

STERLING METALS LTD

CO'(i*Hne$) 8*35 C O Y E N T R Y

ADVTOF SIEMENS-SCHUCKERT(CREAT BRITAIN) LTD. 30/34NewBridgeSt-LondonE.C.4Phone Ccnt846l

INDEX TO ADVERTISERS

MAY, 1 9 3 5

PAGh PAGE

A lum inium P la n t & Yessel Co., L td . — Hilger, L td ., A dam —

Amsler & Co., Alfred J . . . — H y d rau lik G .m .b.H . ix

Anglo-American Oil Co., L td . . — I.C .I. M etals, L td . . —

Avery. L td ., W. & T. . — Jo hnson, M atthey & Co., L td . . x v i

Birm ingham E lectric F um aces, L td . iv Leit.z (London), E. . —

Bolton & Sons, L td ., T hom as . . — McGraw-Hill Publishing Co., L td . vi

B ooth & Co. (1915), L td ., Jam es V McKechnie Bros., L td . xix

B ritish A lum inium Co., L td ., The iii M artin, W . E . & Co., L td . viii B ritish Commercial Gas Assoc., T he . — M etropolitan-V ickers, L td . —

B ritish M etal C orporation, L td ., The . xix Mills, L td ., W m. —

B ritish Oxygen Co., L td ., The . . viii M urex, L td . —

Brookes (O ldbury), L td . . . — N atio n al Alloys, L td . —

B rookland, J . L. . — N o rth e rn A lum inium Co., L td . . vii

C arborundum Co., L td ., The .xviii Oertling, L td ., L. X

Consolidated T in Sm elters, L td . . — P earson, L td ., E . J . & J . —

D em ag A.G. . . . — P erfecta Gas T h erm o stats, L td . —

E bonestos In su lato rs, L td . . — P itm a n & Sons, L td ., Sir Isaac . — Electric R esistan ce F u m ace Co., L td — Priestm an, L td ., J . J . XX Electroflo M eters Co.,- L td . — Ratcliff (Metals) L td ., J . F . xiv E lliott Bros. (London), L td . . — Siem ens-Schuckert (G t. B ritain ) L td . xiii E lton, L evy & Co., L td . . — S.O.S. P a te n ts Co., L td . . — E y re S m elting Co., L td ., T he . — S tein & Co., L td ., J o h n G. ii F o rd ath Engineering Co., L td . . . — Sterling M etals, L td . xii

F oster In stru m en t Co. . — S tew arts an d Lloyds, L td . —

F o u n d ry Services, L td . xi T herm al S yndicate, L td . . xii

F r y ’s M etal F oundries, L td . . — W atson & Sons, L td ., W . — G eneral E lectric Co., L td .

.

H igh -D u ty Alloys, L td . . xi Zeiss (London), L td ., Carl X

seal of quality

. . . . aftercareful inspection, gauging and testing ; when everybody is quite satisfied thatthefinished metal isupto standard, each roli is tightly coiled to protect the inside and the Ratcliff quality seal

“ R ” is afFixed.

• L U S T E R R O L L E D C O P P E R , B R A S S , D IP P IN G , G IL D IN G A N D C A R T R ID G E M ET A L, P H O S P H O R B R O N Z E , ETC .

J. F. RATCLIFF (METALS) LTD., NEW SUMMER STREET, BIRMINGHAM

T e le p h o n e : A sto n C ro ss 3576/7. T e le g ram s: “ R o d en t, B irm in gh am .”

... and finally ... a

x i v

S P E C I A L F U R N A C E S

The i l l u s t r a t i o n s h o w s a r o t a r y drum type non- ferrous annealing furnace for con- tinuous annealing o f s m a l i com-

TO SIIIT SPECIA L REQUIREMENTS ™ m Pie

of the numerous special equipments designed and madę to suit particular re q u i re m e n t s.

W I L D - B A R F I E L D E L E C T R I C F U R N A C E S

L T D . - E L E C F U R N W O R K S - N O R T H R O A D - H O L L O W A Y - L O N D O N - N .7

S T A Y B U T E S T I r l f L

GAUZIf ^and WIRE

Sen/ ta-day fo r this descriptive Publica-

tion No. 80.

The process of drawing fine “ S ta y b rite ” Steel wires has been rapidly developed some time past and Johnson Matthey have been supplying fully annealed wires with a mirror-like finish down to '0005" dia. They have specialised in gauzes woven from these fine wires, and offer “ St ay br i t e ” Steel w ire woven into all the forms into which other materials can be woven. Owing to the great strength of this wire, even when fully annealed, a lighter, and, therefore, more economical, gauze can often be used.

“ Staybrite ” steel gauze and wire are invaluable in most i n d u s t r i e s b e c a u s e o f t h e corrosion-resisting property of the metal.

JOHNSON MATTHEY & ■ CO. LTD.

73/63. HATTON GARDEN, LONDON E.C.I.

E d i t o r i a l O f f i c e : 36 Yictoria Street,

London, S.W .l.

TELEPHONE:

Yictoria 2320.

Editor:

G. SHAW M.Sc., F

T H E

Monthly Journal of the

STITU TE OF ET A LS

ADVERT1SING De p a r t m e n t : T . O . S c o t t & S o n ,

L td.

63 Ludgate H ill, London, E.C.4.

TELEPHONE:

C i t y 4211 (2 lines).

Assistant Editor:

S. O. GUILLAN.

Y olu m e M A Y, 1935 P a r t 5

CONTENTS

In stitu te N ew s and A n n o u n c e m e n t s ...

Personal N o tes . . . • • • • * •

E ducational T o u r to G erm any . F ilm Sym posium on W elding

Papers to be Read at the A u tu m n M eeting :

7 0 1 . “ O bservations o f th e P orosity and Segregation o f T w o B ronze In g o ts.” By N . P . A llen, M .M e t., D .S c ., and S . M . P u d d e p h a t, B .Sc.

7 0 2 . “ C orrosion Below D iscontinuous O xide C oatm gs, w ith Special Reference to M ag n esiu m .” By K . G . L ew is, M .S c ., and U . R . Evans, M .A ., S c.D .

A p p o in tm en is R eąu ired and V acant . . . . A u th o r In d ex to “ M etallurgical A bstracts " .

M ETA LLU R G IC A L A B S T R A C T S I .

I I . I I I . IV .

V.

V I.

V I I . V I I I . I X . X . X I . X I I . X I I I . X IV .

X V . X V I.

X V I I . X V I I I .

Xix.

X X . X X I . X X I I . X X I I I . X X IV .

M a c ro g ra p h y ; C ry sta l S tru e - P ro p e rtie s o f M etals

P ro p e rtie s of A lloys S tr u e tu r e (M etallo g rap h y

tu r e ) . . . . • • • • •

C o rro sio n . . . • • ■ • •

P ro te c tio n (o th e r t h a n E le c tro d e p o sitio n )

E le c tro d e p o s itio n . . . • • • • , ' E le e tro m e ta llu rg y a n d E le c tro c h e m is try (o th e r th a n E le c tr o ­

d ep o sitio n ) . ■ • • • • •

R efin in g

A n a ly sis . . . . • ■ • • •

L a b o r a to r y A p p a r a tu s , I n s tr u m e n ts , & c.. . • , P h y s ic a l a n d M ech an ical T e s tin g , In s p e c tio n , a n d R ad io lo g y T em p eratu r© M e a su re m e n t a n d C o n tro l . . . . F o u n d r y P ra o tic e a n d A p p lian c es .

S e c o n d ary M etals : S c ra p , R e sid u es, &c.

F u rn a c e s a n d F u e ls . ; ■ • • R e fra e to rie s a n d F u rn a c e M a terials .

H e a t- T r e a tm e n t . . . • • • ■ •

W o rk in g . . . . • ■ ■ • •

C leaning a n d F in ish in g

J o in in g . . • •

I n d u s tr ia l U ses a n d A p p lic a tio n s . .

M iscellaneous . .

B ib lio g ra p h y . . . - • • • •

B o o k R ev iew s . . . ■ • • • ■

PAGE

207 208 208 210

211

221 239 240

197 212 220 226 231 235 238 241 241 245 246 249 250 252 252 255 256 257 259 260 261 265 265 271 T h e m o n th ly issu e of M etallurgical A bstracts m a y b e c u t u p fo r c a rd ind ex es, a s m em b e rs w ill receiv e e a rly in 1936 th e y e a r ’s a b s tr a c ts in b o u n d form .

x v i i

Carborundum Brand Refractories

For Clinker'Proof Linings of Boiler Furnaces.

C arb o frax Brick.

C arbofrax - B ernitz air- cooled Blocks.

For Melting Non - Ferrous Metals.

C arb o ru n d u m Crucibles.

For theL iningof Non-ferrous Melting Furnaces.

C arbofrax Brick.

C arb o frax C em ents.

C arb o ru n d u m F iresand.

For Setting of Brick and Tile.

C arbofrax C em ent.

A cement to meet every condition.

For Enamelling Furnaces.

C arbofrax Muffles.

For Potteries.

The C arbo - R adiant Oil- F ired Kiln.

For greater Efficiency from H eat Treating Furnaces.

C arb o frax H earth Tiles.

For Recoyery of W aste H eat.

The C arb o frax R ecuperator.

In other words, a Carborundum Brand Refractory for practically every High Temperature Installation.

We are prepared to advise customers on m atters of furnace design relative to the use of Carborundum Brand Refractory Products, or will undertake to design and build complete Furnace Installations.

The Carborundum Com pany Ltd.,

Trafford Park Manchester.

x v i i i

I N S T I T U T E N E W S A N D A N N O U N C E M E N T S

Council N om inations for 1936-1937.

At th e A u tu m n M eeting to b e h e ld in N ew castle-o n -T y n e fro m S eptem - b e r 9 to 12, th e C ouncil w ill p re s e n t a lis t of n a m e s of p erso n s n o m in a te d fo r office in th e y e a r 1936-1937.

I n acco rd an ce w ith th e R ules,

“ A n y te n m em b ers m a y also, a t or before su c h o rd in a ry g en erał m eeting, n o m in a te in w ritin g , w ith th e w ritte n c o n s e n t to a c t if e lected of th e p erson n o m in a te d , a n y d u ły ąualified p erso n o th e r th a n one of th o se n o m in a ted b y th e Council. . .

May L ecture.

A t a G en eral M eeting of th e I n s t i ­ t u te h e ld (b y co u rte sy of th e Council of th e I n s titu tio n ) in th e H a ll of th e I n s titu tio n of M echanical E n g in eers, L o n d o n , on M ay 8, P ro fesso r W . L.

B rag g , F .R .S ., d eliv ered th e T w en ty - F if th A n n u a l M ay L e c tu re o n “ A t­

om ie A rra n g e m e n t in M etals a n d A lloys.” T h e le c tu re w as given befo re a larg e au d ien ce, a n d after- w a rd s m em b e rs m e t fo r lig h t refresh- m e n ts a n d co n v ersatio n .

T h e lec tu re w ill b e p u b lish e d in th e b o u n d v o lu m e of th e Proceedings (V olum e L V I) t h a t w ill b e d e sp a tc h ed n e x t‘ m o n th to all m em b ers w hose su b scrip tio n s a re n o t th e n in a rre a r.

Proposed G eneral Index.

T h e a tte n tio n of m em b ers is d irec te d to a no tice a p p e a rin g on p. 242 of th is issue, re g ard in g th e pro p o sed G eneral In d e x .

A ll m em b ers h a v e receiv ed a cir- c u la r a n d re p ly fo rm w ith reference to th e in d ex a n d a re re ą u e s te d to r e tu r n th e rep ly fo rm w ith o u t delay.

U nless sufficient o rd ers fo r th e in d ex a re receiv ed i n adta n ce, th e w ork c a n n o t b e p u t in h a n d .

M em bers w ho h a v e m islaid th e ir re p ly fo rm s m a y o b ta in a d u p lic a te o n -a p p lica tio n to th e S ecretary .

A n n u al Subscriptions.

W ill m em b ers, p a rtic u la rly th o se resid in g O verseas, b e good en o u g h

2 0 7

to n o te t h a t th e a m o u n t of th e ir su b scrip tio n s (£3 3s., in th e case of m e m b e rs ; £ 1 ls . in th e case of s tu d e n t m em bers) sh o u ld b e re m itte d in tim e to b e receiv ed on o r before J u ly 1, w h en su b scrip tio n s fo r th e n e x t fin an c ia l y e a r becom e d u e ? O nly b y re m ittin g th e ir su b scrip tio n s p ro m p tly c an m em b ers eu su re th e co n tin u e d re ce ip t of th e M o n th ly J o u rn a l, “ P roceedings ” volum es, a n d o th e r p u b lic a tio n s of th e In sti- tu te . P ro m p t p a y m en ł o f subscrip­

tions m eans a substantial sam ng to the In stitu te in postage, bank char ges, and discounts.

M em bership Additions.

T h e follow ing p erso n s w ere elected on M ay 8, 1935 :

A s M embers.

Ad a m, J a m e s N o rm an , B ish o p to n . Ba c h m e t e w, P rofessor E u g en T h eo ­

d or, Moscow, U .S .S .R .

Ba i l l i e u, Clive L a th a m , C.M.G., O .B .E ., M.A., L ondon.

Be l l, W illiam C h arlto n , L o ndon.

Bi r k s, N o rm a n A rth u r, Assoc. M et., L ondon.

Dy b o w s k i, J a ri., W arszaw a, P o la n d . Fr i e d m a n-, L eopold, E d g w are.

Gi e r d z i e j e w s k i, Casim ir, W arszaw a, P o la n d .

Go o d c h i l d, E d m u n d A rth u r, C helm sford.

Ha r r i s, A rnold W illiam E lsm ere, B .Sc,, B irm in g h am .

Hi r s t, T h o m a s B ayliss V erney, L o ndon.

Hu d s o n, H a ro ld E d w a rd , B irm in g ­ h a m .

Ja n n e t t o, N ich o las A n th o n y , Cleve- lan d , O., U .S.A .

Le w i s, W illiam R ich a rd , B .Sc., L o n ­ don.

Ma t t h e w s, H o w a rd D a v id , B .S., E .E ., A ttle b o ro , M ass., U .S.A . Mo r r e l l, E rie , D u rh a m , N o rth Caro-

lin a, U .S.A .

Pl a k s i n, P ro fesso r Ig o r N icolas, Moscow, U .S .S .R .

Wa k e h a m, F r a n k , H a d ley W ood.

A s Stu d en t M embers.

Bl a c k, A rc h ib ald N iel, B . A . , L o n d o n . Pa r k e r, R o n a ld , L u to n .

P E R S O N A L N O T E S E D U C A T I O N A L TOUR

T he E d ito r reguesłs that h is attention be directed to item s o f interest to mew- bers that m ight be included un d er the

“ P ersonal N otes ” heading. A U eon~

tributions fo r the J u n e issue o f the M o n th ly J o u r n a l should reach the E d itor not later than M a y 25.

Dr. N . P . Al l e n, M .M e t., u n til re c e n tly L e c tu re r in M e tallu rg y a t th e U n iv e rs ity o f B irm in g h a m , h a s b een a p p o in te d S enior R e se a rc h M etallu r- g is t in th e R e se arc h a n d D e v elo p m en t L a b o ra to ry o f th e M ond N ick el C om ­ p a n y , L td .

Mb. P . G. Ba m f o b d, B .E ., w ill s h o rtly b e o n six m o n th s ’ leav e of absence fro m C h ristch u rc h , N ew Z ealan d , a n d corresp o n d en c e m a y be s e n t to h im u p to N o v e m b e r 30 a d d ressed B M /A M H S , L o n d o n , W .C .l.

M b. Al f b e d Ch e s t e b Be a t t y h a s b een a w a rd e d th e gold m e d a l of th e I n s titu tio n of M ining a n d M etallu rg y , th e h ig h es t h o n o u r w h ich i t is in i ts p ow er to b esto w , in reco g n itio n of h is d istin g u ish e d services to th e m in in g in d u s try , a n d of h is far- sig h ted v isio n a s a m in in g en g in eer in th e d ev elo p m en t of m in e ra ł de- p osits, w ith p a r tic u la r reference to th e co p p er reso u rces of N o rth e rn R h o d esia.

Pb o f e s s o b G. H . St a n l e y, D .S c., A .R .S.M ., C o rresponding M em b er to th e Council fo r S o u th A frica, h a s b e en a p p o in te d D ire cto r of th e new M inerals R e se arc h L a b o ra to ry , U ni- v e rs ity of th e W itw a te rs ra n d , Jo h a n - n esb u rg , S o u th A frica, fo r th e e s ta b ­ lis h m e n t a n d o p e ra tio n o f w h ich a special g r a n t of £6000 h a s b e en m ad e b y th e G o v e rn m en t M ines D e p a r t­

m e n t. \

O bituary.

Pb o f e s s o bW . R . E . Ho d g k i n s o n, C .B .E ., P h .D ., M .A., d ied a t h is residence in B la c k h e a th o n A p ril 8 a t th e ag e of 83 y e ars. P rofessor H o d g k in so n w as a n O riginal M em ber of th e I n s titu te a n d , w ith o n e excep- tio n , its o ld est m em b er.

2 0 8

t o g e r m a n y

F o r ty s tu d e n ts to o k p a r t in th e I n s t i t u t e ’s seco n d E d u c a tio n a l T o u r, w h ic h th is y e a r to o k p lace in G er­

m a n y a n d la s te d fro m A p ril 7 t o 16.

T h e to u r w as a rra n g e d in c o -o p era ­ tio n w ith th e N a tio n a l U n io n o f S tu d e n ts a n d w as e v en m o re s tre n u - o u s th a n th e B elg ian T o u r la s t y e ar.

A a ch e n , Cologne, a n d D u s se ld o rf w ere t h e th r e e m a in c e n tre s fro m w h ic h th e v a rio u s tr ip s w ere m ad e . I n b e tw ee n th e v a rio u s w o rk s’ v is its , m a n y p lac e s o f o th e r t h a n p u re ly te c h n ic a l in te r e s t w ere seen o r v isite d . T h e w hole to u r w as sp le n d id ly a rra n g e d , n o t a m o m e n t w a s w a ste d , a n d e v e ry th in g fo r w h ic h G e rm an y is re n o w n e d w as e n jo y e d to th e u tm o s t in th e s h o r t tim e a v a ilab le.

T h e foliow ing w o rk s a n d in s titu - tio n s w ere v is ite d :

Technische H oehschule, A a ch en .—

L ik e all G e rm an T ec h n ical H ig h S chools, th is r a n k s e ą u a lly h ig h w ith t h e U n iv e rsitie s a n d i t is in te re s tin g t o n o te t h a t th e d e m a n d in G e rm an y fo r tr a in e d sc ientific m en is so g re a t t h a t s tu d e n ts o f th e H o ch sch u le can ó b ta in a p p o in tm e n ts befo re th e y h a v e c o m p le te d t h e ir c o u rses. T h e p a r ty w as sh o w n o v e r th e N e u m a n n I n s ti- t u t , w h ic h com prises th e m e ta llu r- gical se c tio n s o f t h e H o c h sc h u le. I n a d d itio n to th e tra in in g p ro v id e d , a g r e a t d e al o f re sea rc h is c a rrie d o u t h e re w ith t h e h elp o f m ag n ifice n t a p p a r a tu s a n d e ą u ip m e n t. T h e M asch in en L a b o ra to riu m a n d D e- p a r tm e n ts o f P h y sic s a n d E le ctro - te c h n ic s w ere also in sp e cted .

A s te n & L y n e n , Stolberg.—T hese a re t h e o ld e s t b ra s s w o rk s in th e w o rld , b u t a lth o u g h o f su c h h isto rie in te r e s t, a re c o m p le te ly m o d ern ized . M e tal w as b ein g m e lte d in gas-fired o r electric fu rn ac e s a n d c a s t in to J u n k e r w a ter-c o o le d m o u ld s. H o t- ro llin g o f b ra s s a n d b rig h t-a n n e a lin g w ere in ac c o rd an c e w ith la te s t p ra c- tic e . M uch h a n d -sp in n in g o f b ra ss a rtic le s w as also b ein g c a rrie d o u t.

D urener M etallw erke A .G .— H e re a re p ro d u c e d lig h t allo y s o f th e D u ra lu m in t y p e a s w ell a s h e a v y n o n - fe rro u s a llo y s. L a rg e e x tru s io n p resses w ere seen in o p e ra tio n to -

Educational Tour to Germany

g e th e r w ith h o t-fo rg in g , s ta m p in g , a n d rolling.

F elten & G uilleaum e Carlswerk A .G .—A n e n o rm o u s w o rk s p ro d u c in g a n a s to n is h in g v a rie ty o f a rtic le s on th e one fa c to ry s ite — fro m n a ils a n d w ire -n e ttin g to ele ctric cab les a n d ste el cables fo r m in e s a n d su sp en sio n b rid g es. Som e o f t h e m a n u fa c tu rin g processes w ere seen to g e th e r w ith th e te s tin g o f a s tr a n d e d s te e l cable,

m a n n p ro cess, a n d th e m a n u fa c tu re o f lo co m o tiv e fire-boxes.

Forschungslaboratorium der V er - einigten Stahlw erke A .G .— T h is w as a n o th e r m ag n ifice n t re se a rc h o rg a n - iz a tio n . A m o n g st o th e r th in g s show n w ere fa tig u e te s tin g m a c h in e s,to rsio n a n d b e n d in g te s ts , im p a c t ten sile te s ts o n c h ain s, th e L o sen h au sen p u ls a to r, creep te s ts , a n d corrosion t e s ts .

T h e G erm an g u id es a n d som e o f th e p a r ty a f te r v is itin g th e w o rk s o f F e lte n & G uilleaum e. T h e r e s t o f t h e p a r ty a re in th e b u s.

c a le u la te d to fail a t a d e ad lo ad o f 240 to n s a n d a c tu a lly failin g a t 239 to n s.

K a ise r-W ilh e lm In s titu t f u r E isen- fo rsc h u n g , D usseldorf.—T h e d e m a n d in G e rm an y fo r re se a rc h fa cilities is so g r e a t t h a t th e I n s t i t u t is h a v in g to rem o v e to a la rg e r e s ta b lis h m e n t. I n s p ite o f th is , th e re m a in in g a p p a r a tu s a n d e q u ip m e n t w as v e r y im p re s- sive.

Vereinigte Deutsche M etallw erke, D uisburg.— H e re w ere seen th e ex- tru s io n o f n o n -ferro u s sectio n s, th e p ro d u c tio n o f tu b e s b y th e M annes-

D ortm under U nion B rauerei A .G .—

T h e “ h ig h s p o t ” o f th e to u r in m o re w ay s t h a n one. A fte r ex am in in g m eta llu rg ic a l a s p e c ts o f th e p la n t th e p a r ty w as in v ite d to a “ K n e ip e ” (E n g lish tra n s la tio n : a “ l e t u p ” ).

F ried . K r u p p A .G ., E ssen.—T he m o s t e x te n siv e w o rk s v isite d . B last- fu rn ac e s a n d t h e m a n u fa c tu re o f ste el w ere in sp e c te d to g e th e r w ith th e fo rg in g o f a 1 0 0-to n ste e l b ille t in a 15,000-ton p re ss, a m o s t im p ressiv e sp e c ta cle .

J . A . H enckel, Solingen.—T h e fa m o u s “ T w in ” b r a n d k n iv es, scis-

Educational T our to Germany

so rs, & c., w ere seen in c o u rse o f m a n u fa c tu re , c o n sid erab le a d m ira tio n b ein g a ro u sed fo r th e h ig h d e g ree o f c ra fts m a n s h ip in v o lv ed .

T h e p re d o m in a n t im p ressio n g a in e d fro m th e to u r w as th e im m en se im - p o rta n c e w h ich G erm an in d u s tr y a tta c h e s to scientific re se a rc h a n d th e u tm o s t u se w hich is m a d e o f all tec h n ica l a n d o th e r reso u rces.

G re a te s t th a n k s a re d u e t o th e D ire cto rs a n d S ta ff o f t h e v a rio u s firm s fo r th e ir c o u rte sy , tro u b le , a n d su p e rb h o s p ita lity , a n d a lso t o M essrs.

D o ck h o rn a n d R u s c h k a m p w ho so successfully c o n d u c te d t h e p a r ty th r o u g h o u t th e G e rm an p a r t o f th e T o u r.— A . B .

In te r n a l S tresses in M etals an d A lloys.

Dr. Ha r o l d Mo o r e, C .B .E ., P re si- d e n t o f th e I n s t i tu t e , w ill d e liv e r th e seco n d a n d t h ir d o f th r e e le c tu re s on t h e a b o v e s u b je c t, u n d e r t h e au sp ices o f th e C o m p an y o f A rm o u re rs a n d B rasiers, o n M o n d ay , M ay 20, a n d M onday, M ay 27, a t th e Sir J o h n C ass T ech n ical I n s t i tu t e , 31 J e w ry S tre e t, A ld g a te , L o n d o n , E .C ., a t 7 p .m . A dm issio n is free , w ith o u t tic k e t. All m em b e rs o f t h e I n s t i tu t e a n d th e ir frie n d s w ho m a y b e in te r- e s te d in t h e s u b je c t a re c o rd ia lly in v ite d to a tte n d .

A b stractin g Service.

A u th o rs o f p a p e rs , b o o k s, o r te c h n ic a l a rticle s o f d ire c t o r in d ire c t in te r e s t to t h e science o r p ra c tic e o f n o n -ferro u s m e ta llu rg y , a re re ą u e s te d to fo rw a rd copies to t h e I n s t i tu t e in o rd e r t h a t th e a b s tr a c tin g a n d review serv ice m a y b e m a d e c o m p le te . L oose copies a re also fo u n d to b e o f v a lu e in th e L ib ra ry .

T h e I n s t i tu t e ’s lib ra ry d esires to be p lac ed o n m ailin g lis ts to receiv e copies o f n o n -ferro u s m eta llu rg ic a l trad e lite ra tu re fro m all p a r ts o f th e w o rld .

Copies o f u n p u b lis h e d theses a re a lso r e ą u e s te d , for p e rm a n e n t p r e ­ se r v a tio n in th e I n s t i tu t e ’s lib ra ry .

P e r io d ic a l: “ M etals an d A lloys.”

A c o p y o f t h e F e b ru a ry , 1935, issu e o f M eta ls a n d A llo y s is r e ą u ir e d to c o m p le te th e I n s t i t u t e ’s L ib r a r y file.

W ill a n y m e m b e r w ho is p re p a re d to g iv e o r sell a co p y o f th is issu e k in d ly c o m m u n ic a te w ith th e L ib ra ria n ? C opies o f th is issu e a re n o t o b ta in a b le n o w fro m t h e p u b lis h e r.

F ilm Sym posium on W elding.

T o a ffo rd v is ito rs to L o n d o n a n o p p o r tu n ity to a c ą u a in t th em se lv es w ith th e im p o r ta n t a d v a n c e s w hich h a v e b e en m a d e in w eld in g , B ritis h I n d u s tr ie s H o u se E n g in e erin g S ection h a s a rra n g e d a d isp la y o f film s, ac- c o m p a n ied b y c o m m e n ta rie s , to b e h e ld o n M ay 22 a n d 29, 1935, b e tw ee n t h e h o u rs o f 5 a n d 7 p .m . P e rso n s in te re s te d m a y a s k ą u e s tio n s , w hich w ill b e a n sw e re d b y t h e e x p e r ts w ho w ill b e in a tte n d a n c e d u rin g th e film d isp la y . T h e film s w ill p rim a rily r e p re s e n t p ro g re s s th ro u g h o u t th e U n ite d K in g d o m a n d D om in io n s, b u t w ill also e m b o d y fe a tu re s o f sp e cial in te r e s t fro m o th e r p a r ts o f t h e w o rld .

A t e a re c e p tio n w ill b e h e ld in B ritis h In d u s tr ie s H o u se C lubroom s, M arb le A rch, W .l , b e tw e e n 4 a n d 5 p .m e ac h a fte rn o o n . T h e film s a re b e in g sh o w n b y t h e c o u rte s y o f : A c ety len e a n d W eld in g C o n su ltin g B u re a u , L td ., L o n d o n ; B ritis h O xy g en C o m p an y , L td ., L o n d o n ; a n d M urex W eld in g P ro cesses, L td ., L o n d o n . I t is h o p e d t h a t a rra n g e - m e n ts m a y also b e m a d e fo r p ra c tic a l d e m o n s tra tio n s . A p p lica tio n s for tic k e ts , m e n tio n in g th is J o u rn a l refere n ce, sh o u ld b e a d d re ss e d t o : M r. G u y F . D o w d in g , A .M .I.M ec h .E ., M a n ag er, E n g in e e rin g S ectio n , B ritis h I n d u s tr ie s H o u se, M arb le A rch , L o n d o n , W . l .

2 1 0

PAPER No. 701. This p a p er is copyright. I t m ay be rep rin ted , wholly or in p a rt, in th e Press (w ith due aclcnowledgment) a fte r being presented a t th e A u tu m n M eeting of th e I n s titu te to be held on Septem ber 9-12, 1935, in Newcastle-upon-Tyne. The In s titu te as a body is n o t responsible fo r th e statem e n ts or opinions expressed in th is paper, on which w ritten discussion m a y be sen t to th e S ecretary n o t la te r th a n O etober 1, 1935.

This paper will not be reissued in the form of a separate “ Advance Copy,” a method of publication which has been discontinued.

OBSERVATIONS OF TH E POROSITY AND SEGREGATION OF TWO BRONZE INGOTS.*

B y N. P . A L L E N ,t M.Met., D.Sc., Mem b er, an d S. M. P U D D K P H A T 4 B . S c . , Me m b e r.

Sy n o p s i s.

The distrib u tio n of porosity and th e variatio n in copper co n ten t in two 1 0 per cent. tin -b ro n ze ingots have been found to b e influenced princi- pally b y th e flow of h e at during solidification. T here was a close connec- tion betw een th e porosity and segregation of th e ingots.

In t r o d u c t i o n.

I n

a previous paper1 the processes leading to the formation of cavities in an ingot were discussed, and reasons were given for oonsidering the phenomenon of inverse segregation to be largely the result of the same processes. The present work was undertaken in order to study further the distribution of porosity in ingots, and to obtain more evidence on the relationship between porosity and segregation.

Pr e p a r a t i o n o f In g o t s.

Two ingots were cast from separate quantities of bronze made in the following way : 29 Ib. of cathode copper was melted under a deep layer of oharcoal in a gas-fired crucible furnace, and 3J lb. of “ Chempur ” tin was added to it. The alloy was stirred thoroughly_with a carbon rod, and cast at 1100° C. into a heavy copper mould, dressed with bone ash, and preheated to about 90° C. The metal was poured from the crucible in the ordinary way, the lip of the crucible being rested on the top of the mould, and a steady stream being maintained such th at the mould was filled in about 20 seconds.

The mould was th a t described in the former paper. One ingot was cast with the wide end upwards, and the other with the narrow end upwards, and both were fed with the liquid metal remaining in

* M anuscript received F eb ru a ry 16, 1935.

f L ectu rer in M etallurgy, U niversity of Birm ingham , j M etallurgical D ep artm en t, U niversity of Birm ingham .

Note to Abstractors and Other Readers.—This paper will be published, in perm an en t form , in th e Journal o f the Institute o f Metals, VoI. L V II, 1935.

Reference should aceordingly be as follow s: J . ln s t. Metals, 1935, 57 (Adyance

c°py)-

3 1 1

701

A llen and P u d d e p h a t: Observations o f the

tłie crucible. They weighed about 28 lb. each, and were 9 | in. long, 3§ in. square at the wide end, and 2 | in. square a t the narrow end.

The ingot cast wide end upwards had an average copper content of 89-39 per cent. and the other an average copper content of 89-94 per cent.

Ex a m i n a t i o n o f In g o t s.

A slab | in. thick was cut vertically from the middle of each ingot, and, after it had been planed and its macrostructure examined, it was cnt np in the manner shown in Fig. 1.

The densities of all the pieces were determined by Archimedes’s method. The figures reported are the apparent densities in water

a t 15° C., and are accurate within

± 0-0 1.

Some exception has been taken to the use of density determinations in the study of the porosity of bronze, on the ground th at the density of bronze is liable to vary, independently of the number of cavities present, on account of the varying quantities of eutectoid con- stituent which may be present.

Whilst the metallographic prin- ciple involved is perfectly sound, its application to bronze is un- necessary, as it is elear from the values plotted in Fig. 2, th a t the densities of the a solid solution and the eutectoid are, within very close limits, the same. G. L. Bailey 2 and others who have reported results demonstrating the effect of casting temperature on the density of cast bronze, have, in fact, studied the efiect of casting temperature on its porosity.

In order to determine the naturę of the segregation, samples taken from about half the density pieces were analyzed for copper content by an electrolytic method similar to th a t devised by R. A. F. Ham ­ mond.3 The method was thoroughly tested. Six analyses of a standard sample agreed to within + 0-01 per cent. of copper, and the same order of agreement was obtained in several check analyses in the course of the work. I t is considered th a t when all other errors are taken into account, variations of 0-04 per cent. must be regarded as significant,

2 1 2

A B C

D

E s

1 4 -

1 -f)

¥

«-

i

i

- e -

4

f

( - 1

F

r I < - - f

G

l

H ^-

i

j

L

Fi g. 1 .

Samples from many parts of the ingots were examined micro- scopically.

Ob s e r v a t i o n s.

The macrostructures of the ingots were normal. . Columnar crystals up to \ in. in length had grown at the bottom and at a few places along the sides of the ingots, and elsewhere fine equi-axed crystals were present, and were smallest near the top.

The results of the measurements of density are plotted in Fig. 3.

Both ingots were porous and had rather poor surfaces. Except where skin porosity was present, the density of the materiał in both ingots decreased regularly from the outside to the centre, and the density contours were generally symmetrical, and followed the shape of the ingot fairly closely. The oone of relative soundness found in copper and aluminium-copper alloy ingots was absent, though a t the

Porosiły and Segregation o f Two Bronze Ingots

T I N . P E R C E N T

Fi g. 2 .—D ensities of Copper—T in Alloys. T he figures are th e ap p aren t densities in w ater a t room tem p eratu re of 30 grm . ingots of th e alloys m elted in fireclay boats a t 1150° C. in dry nitrogen, and allowed to cool w ith th e furnace.

bottom of the ingot cast wide end upwards the diflerence of density between the outside and the centre was quite smali.

The mould taper had a very marked influence on the distribution of porosity. Whereas in the ingot cast wide end upwards the most porous materiał was confined to a cone in the upper part of the ingot, casting narrow end upwards resulted in the axis being very porous nearly all the way down.

Fig. 3 also shows the distribution of copper in the ingots. Differences as great as 1 per cent. were found. The segregation was inverse, and the contours of copper content, like those of density, were parallel to the sides of the ingots, except a t the bottom, where they were turned inwards to form a smali cone of tin-rich materiał. Except where there was skin porosity the materiał having the highest tin content had also the highest density. The relationship between density and copper content is shown graphically in Fig. 4. The two variables followed each other very closely, except at the bottom of the ingot cast wide end upwards, in which a variation of composition occurred .without a corresponding change of density.

2 1 3

A llen and P uddephat: Observations o f the

2 1 4

Fig. 3.—DistributionofPorosity and Segregation,

There was no relationship between the segregation and the macro- structure.

Di s c u s s i o n o f Re s u l t s.

The relationship between porosity and copper content is such that the distribution of both can be accounted for by a fłow of tin-rich liquid in th e . directions indicated by the arrows in Fig. 1. This will explain completely the ingot cast narrow end upwards,. I t seems th a t a t a relatively early stage of solidification a bridge of dendrites

Porosity and Segregatian o f Two Bronze Ingots

was formed across the ingot about a ąuarter of the way down, and that the mass of liquid thereby entrapped in the centre subsequently fed the ingot in all directions. The “ heat centre ” of the ingot (about two-thirds of the way down the axis) conseąuently became extremely Iow both in density and in tin content.

Broadly, the behaviour of the ingot cast wide end upwards was similar, but in this case the downward movement of liąuid was not restricted until a comparatively late stage of the process of solidification, so th a t there was a continuous increase of tin content and density down the axis.

2 1 5

Allen and P u d d ep h a t: Obsewations o f the

The conditions a t the bottom of this ingot require special attention.

The variations of density in this region are misleadingly smali on account of the skin porosity, but even when this is taken into account, they are much less than in other parts of the ingot. This is probably due to the excellent feeding of the bottom of the ingot. The porosity of an ingot is the resultant of two factors, the gas content, and the drop of pressure caused by contraction.4 From the densities prevailing on the outside of the ingot (where skin porosity was absent) it appears th at the gas content of the metal was such th a t when the metal froze under such conditions no drop of pressure due to contraction was ex- perienced, the density was about 8-3-8-5. As long as feeding was

perfect uniform densities of about this value were obtained, and these conditions prevailed in the zone outside the 8-3 density con- tour. If a region in this zone, but a little removed from the edge be considered, it will be seen that, once solidification has begun, it both feeds tin-rich liąuid to the outside and receives it from the centre (Fig. 5, A, B ).

The liąuid it receives, however, will be lower in tin than th at which it loses, as solidification is less advanced towards the centre, so that, on balance, it will gain less tin than its neighbour on the outside. Conseąuently there will be inverse segregation without any marked density change.

This conception will also explain the tin-rich cone a t the bottom of both ingots, for metal in the neighbourhood of A (Fig. 1) feeds the contraction in two directions and therefore loses an abnormal amount of tin-rich liquid, receiving in compensation (only) liąuid poorer in tin from the centre. The finał result is an abnormal loss of tin which is the counterpart, in inverse segregation, of the familiar “ ingot corner segregation.”

Mi c r o s t r u c t u r e s.

The cavities were inter-dendritic in character and associated, as would be expected, with the a-8 constituent.

Special attention was paid to the distribution of the oc-8 constituent, on account of the observations reported by F. Johnson in discussing a previous paper.1 The particie size of the constituent increased from

216 F i e . 5.

Pl a t ę I .

2 1 7

'

,

M ,..

: 1

Porosiły and Segregation o f Two Bronze Ingots side to centre of the ingot, which made it difficult to estimat.e the relative ąuantity, but after careful comparisons at many magnifications, it was concluded th at over the greater part of the ingot there was no perceptible difference in amount. Nevertheless, there was a narrow border not more than 0 1 -0 2 cm. wide round the edge of the section in which the particles were both very minutę (0-001 cm. diameter) and decidedly less in ąuantity, and to this extent Johnson’s observation was confirmed.

At the extreme edge a crust about 0-01 cm. thick of materiał very rich in eutectoid constituent was found. This crust was so narrow that it was easily rubbed away during preparation of the specimen, and it was found only in specimens mounted in Bakelite. The typical appear- ance is shown in Fig. 6 (Platę I). The formation was not an exudation from the surface, as the a - 8 constituent was quite fłush with the a, nor was it materiał thrust through from the centre, as observed by Genders,5 for there were no streaks of a-8 constituent leading to the centre. On the contrary, it was most marked where the band of materiał poor in a-8 constituent was widest, and these two formations appeared to be related. The outline of the primary dendrites of a constituent freąuently suggested th at solidification had been completed by the growth of crystals towards the edge, a process which is possible if it be assumed th at some degree of under-cooling took place, and th at the first nuclei appeared, not quite a t the edge, but at a little distance within the metal.

The formation is mentioned on account of its metallographic interest.

Its scalę was so smali th at it could scarcely have aflected the mass segregation as determined by the analyses reported here.

CONCLUSIONS.

(1) In chill-cast 10 per cent. tin-bronze ingots the distributions of cavities and copper is determined by the flow of heat away from the casting, in such a way th a t the parts of the ingot which solidify last are most porous and richest in copper.

' (2) Both distributions are largely explicable on the assumption th a t during solidification a liquid rich in tin travels towards the outside of the ingot.

(3) In this case, contraction during solidification was the principal cause of the movement.

Ac k n o w l e d g e m e n t s.

The authors desire to express their thanks to Professor D. Hanson, D.Sc., who provided facilities for carrying out the work, to the British

219

Porosity and Segregation o f Two Bronze Ingots Non-Ferrous Metals Research Association for the loan of the mould, and to Mr. W. F. Brazener for assistance in preparing the ingots.

Re f e r e k c e s. 1 N. P . Allen, J . In st. M etals, 1 9 3 3 , 52, 1 9 3 . 2 G. L. Bailey, J . In st. M etals, 1 9 2 3 , 30, 4 0 1 . 3 R . A. F . H am m ond, J . In st. Metals, 1 9 2 7 , 3 7 , 2 6 8 . 4 N. P. Allen, J . In st. M etals, 1 9 3 2 , 49, 3 1 7 . 6R . Genders, J . In st. Metals, 1 9 2 7 , 3 7 , 2 4 1 .

220

PAPER No. 702. This p a p er is copyright. I t m ay be rep rin ted , wholly or in p a rt, in tlić Press (w ith duo acknow ledgm ent) a fte r being presented a t th e A utum n M eeting o£ the In s titu te to be held on Septem ber 9-12, 1935, in N ew castle-upon-Tyne. The In s titu te as a bo d y is n o t responsible fo r th e statem en ts or opinions expressed in th is paper, on which written discussion m ay be sen t to the Secretary n o t la te r th a n O ctober 1, 1 9 3 5 . This paper will not be reissued in the form of a separate “ Advance Copy,” a method of

publication which has been discontinued.

CORROSION BELOW DISCONTINUOUS OXIDE COATINGS, W IT H SPECIAL REFER EN C E TO MAGNESIUM.*

B y K . G. L E W IS ,t M.Sc., Membek, and U. R . E V A N S,f M.A., Sc.D., Membek.

Sy n o p s i s.

P ro tectiv e processes fali in to tw o classes : (a) safe processes, where even incom plete tre a tm e n t lengthens th e tim e of p erforation; (6) dan- gerous processes, w here inad eq u ate trea tm e n t intensifies a tta e k and brings ąu ick er perforation th a n no trea tm en t.

M agnesium, uncoated and coated w ith oxide layers produced by th ree different trea tm e n ts applied for num erous different periods, has been sub- jected to sodium chloride in a new circulating apparatus. Tim e-corrosion curves an d perforation periods have been obtained. The d a ta show th a t these processes belong to th e ‘ ‘ safe ” class.

The valu e of a n y p ro tectiv e treatm en t depends n o t so m uch on its

power to prevent attack where the treatment has been perfect, as on the happenings at points where the treatment has been originally insufficient or subseąuently damaged. The studies of metallic coats1 and paint coats,2’ 3>4- 5 conducted in the authors’ laboratory, have been concentrated mainly on phenomena at points where, of intention, the coating has been (a) applied so sparsely as to present discon- tinuities,

metallic base. In exceptional cases, protection has been observed even at points where the metal was freely exposed to the corrosive agent. More often corrosion has been observed at the discontinuity, and, in exceptional circumstances, the attack has been locally more intense than if no coating were present. The idea, still prevalent to-day, that a faulty coating of a cathodic ” metal necessarily gives intensified corrosion at the fault, is quite erroneous, and rests on a misnnderstanding of the electrochemical principles involved. Intensi- fication of corrosion by an incomplete “ protective ” operation is, however, not uncommon in water-treatment. I t has been found 6 th at most alkaline inhibitors (sodinm hydroxide, carbonate, silicate,

* M anuscript received F eb ru ary 1, 1935.

f The U niversity Chemical L aboratories, Cambridge.

Note to Abstraotors and Other Readers.—This p a p er will be published, in p erm anent form , in th e Journal o f the Institute of Metals, Vol. L V II, 1935.

Reference should accordingly be as follows : J . ln s t. Metals, 1935, 57 (Adyance copy).

2 2 1

702

Lewis and Evans : Corrosion Below Discontinuous or phosphate), added to a salinę water in sufficient quantity, remove its corrosive power for many metals. If added in insufficient ąuantity, they rednce the area attacked morę than the total destruction of metal, and, sińce the corrosion per unit area of the part affected is thus increased, the time needed for perforation is actually diminished.

Theory indicates th at this danger of premature perforation is to be expected of all inhibitors which act by stifling the anodic reaction, provided th at the velocity of corrosion is determined even in part by the accompanying cathodic reaction; for, in such cases, the area attacked is likely to be diminished more quickly than the total destruc­

tion of metal. If the inhibitor acts by stifling the cathodic change, then there is no reason to expect accelerated perforation.

It is clearly important to distinguish two classes of protective treatm en t:—(a) a dangerous class, where incomplete treatm ent causes intensification of attack and brings about perforation. sooner than it would occur on untreated m etal; and (b) a safe class, where incom­

plete treatment, whilst not preventing attack, at least renders the time needed for perforation longer than th at of unprotected metal.

For many types of protective treatment much of the information necessary to assign processes to one or other class js available; but in regard to protection by oxide coats, there appears to be no record as to whether or not an insufficient coating can cause intensification of attack. Yet oxide coats are to-day largely used in protection, especially on magnesium and aluminium.

Now Whitby 7 and Schikorr 8 consider th at the corrosion of mag­

nesium is controlled, at least in part, by the anodic reaction. Some oxide coats, notably those containing chromium, probably inhibit largely by stifling the anodic reaction, whilst others, notably zinc oxide, inhibit mainly by stifling the cathodic reaction; 9 possibly some treat- ments—for instance, those studied by Sutton and Le Brocq 10—retard both anodic and cathodic reaction. I t is reasonable to hope that, in some at least of the processes available or capable of being worked out, “ incomplete treatment ” would cause no shortening of the per­

foration time. The experiments described below were designed to examine this matter. No attem pt was made to realize in the labora- tory any particular “ seryice conditions” ; rather the conditions of coating and corrosion were made as simple as posśible, so as to obtain a simple answer to fundamental questions.

The work consisted of :

I. Preliminary experiments on producing and testing oxide coats.

II. Development of a simple method for measuring the hydrogen evolution from magnesium specimens with protected edges..

222

Oxide Coatings, with Special Reference to M agnesium III. Experiments on untreated magnesium to study :

(i) the efiect of surface condition ;

(ii) the effect of concentration of salt-solution.

IV. Experiments on finely-ground magnesium pretreated for different periods in a solution depositing oxide coats, using

(a) a new bath, containing zinc sulphate and ammonium

n itra te ;

(b) the bath containing potassium dichromate, alum, and sodium hydroxide, tested by Sutton and Le Brocq; and (c) the bath containing potassium dichromate and sodium

sulphate, tested by Sutton and Le Brocq.

V. Experiments (with bath (a) only) using a rough surface.

VI. Determination of perforation times after treatments.(a),

VII. Interm ittent spray tests, using sea-water on magnesium, treated by processes (a) and (c) and also (d) Bengough and Whitby’s selenium treatment.

Ma t e r i a ł.

The magnesium used was sheet of 99-9 per cent. purity, furnished by the American Magnesium Corporation. The original thickness as rolled was 0-21 mm. (0-0083 in.), which was reduced to 0-20 mm.

(0-0079 in.) after grinding one side only with all emery grades down to

“ 00 ” French emery, and to 0-18 mm. (0-0071 in.) when ground on both sides.

I . Pr e l i m i n a r y Ex p e r i m e n t s.

Numerous trials were made : (a) on magnesium abraded in diiferent m anners; (&) with baths containing zinc, aluminium or lead salts, or a combination of these; (c) in absence or presence of ammonium salts, especially ammonium nitrate; (d) with or without application of cathodic treatm ent; and (e) using fresh or old baths.

It was found that the coats of best appearance did not always give best protection. Certain coats, which were sufficiently compact and uniform to give interference tints, accelerated rather than reduced corrosion, whilst certain lead baths, which gave coats of poor appear­

ance, reduced corrosion considerably in certain circumstances. In the end, for simplicity, the treatment selected for special study was a simple dip, without applied e.m.f., in a vertical position, in a bath containing zinc sulphate solution (50 grm./litre) and ammonium nitrate (50 grm./litre). Dipped in such a bath, the magnesium goes into solution, replacing zinc, not as metal but as oxide (probably hydrated).

The oxide coat has a pearly greyish-white appearance in the early stages, but becomes duller after long dipping.

p 223

Lewis and Evans : Corrosion Below D iscontinuous

■ ilt

A B

I I . Me t h o d o f Me a s t t r e m e n t.

The magnesium sheet was cut into panels 4 in.

3 in., which were shuffled, abraded, and cut to 1 in. sąuares (Fig, 1, A). Pieces

224