The corrosion behaviour of cunifer-10 alloys in seawater-piningsystems on board ship. Part I

NEDERLANDS SCHEEPSSTUDIECENTRUM TNO

NETHERLANDS SHIP RESEARCH CENTRE TNO

ENGINEERING DEPARTMENT

LEEGHWATERSTRAAT 5 DELFT

THE CORROSION BEHAVIOUR OF CUNIFER-10 ALLOYS

IN SEAWATERPIPINGSYSTEMS ON BOARD SHIP

PART I

(HET CORROSIEGEDRAG VAN CUNIFER-1O LEGERINGEN,

TOEGEPAST VOOR ZEEWATERLEIDINGEN AAN BOORD VAN SCHEPEN)

DEEL I

by

JR W. J. J. GOETZEE

Cooperator Corrosion Labdratoiy Royal Netherlands Navy

and

DR. JR. F. J. KIEVITS

Lieutenant commander (E) Head of the Corosion Laboratory Royal Netherlands Navy

RESEARCH COMMITTEE

IL N. PSiiooiw

DR b. F. J.KIEVITs

P. KUIPERS

IR. J. VAN DER Nboiw

Ii. A. DE Moor (ex officio)

De door de economische ontwikkeling in de zeevaart wnselijk geworden vermindering van de exploitatiekosten van het schip heeft o.a. geleid tot de noodzaak de levensduuren bedrijfszeker-héid van de machinekamercomponenten te verhogen.

Een belangrijke component van de machmekamerinstallatie is hot zeewaterleidingsysteem.

De door natuurlijke factoren bepaalde agressieve eigenschap-pen van het milieu waaraan de matenalen van dit systeem zijn blootgesteld is in het verleden aanleiding geweest voor uitvoerig onderzoek gericht op de ontwikkelmg van meer resistente ma terialen.

HoOwel dO thans beschikbare kopernikkel-ijzer

(Cunifer)-legermgen in vergehjkmg met vroeger toegepaste materialen tot vrhoging van de levensduur hebben geleid, voldoet deze in nog onvoldoende mate àan de, om eerder genoemde reden, strenger svordende eisen van de reder.

Om deze redOn werd na een uitvoerig literatuuronderzoek en eeñ enquête inzake de aard en de omvang van het probleem op initiatief van de Koninklijke Marine en rederijen een fundamen-ted onderzoek ingesteld naar hOt mechañisme van de aantasting van pijpmaterialen.

Omdat de toepassing van koper-nikkOl legeringen met 10% Ni en 1,5% Fe in zeewatersystemen tot bomoedigende resultaten heeft geleid werd het onderzoek op dit matenaal gencht

Ret doel van het onderzoek is het vaststellen van behandehngs

bewakings- en ontwerptechnieken, die tot verbetering van de

1e'ensdütir van het systeem leiden. In dit rapport worden, na een beschouwing over de criteria, die bij de materiàalkeuze moeten worden gehanteerd en de Cisen die aan het materiaal in het zee-watersysteem worden gesteld, aismede over de verschillende cor-rosie-aspecten, liet verrichte ondei-zoek en de resultaten vermeld. Deze eerste fase van het onderzoek was gericht op de invloed van warmtebehandeliñg en de bed±ijfscondities op het ontstaan en het gedrag van de beschermende laag waaraan de corrosie resistentie van het rnateriaal moet worden toegeschreven.

Tevens werd met een fundamenteel onderzoek mzake de struc

tuur van deze laag een begin gemaakt Dc conclusies werden

sarnengevat in hoofdstuk 4, tersvijl in hoofdstuk 5 de voortzetting van het onderzoek wOrdt vermeld.

NEDERLANDS SCHEEPSSTUDISCENTRTJM TNO

The economical development in shipping industry necessitates to a decrease of maintenance and repaircosts of machinery com-ponents.

An important component of the machinery is the seawater

piping system. The corrosive and erosive properties of seawater to which the piping material is exposed has led in the past to ex-tensive investigations aimed at the development of more resistant materials.

Although the Cunifer aIloy now available have increased life-time of piping system considerably, thO requirements of ship-owners are not yet fulifilled sufficiently for reasons mentioned above.

On the initiative of the Royal Netherläñds Navy and

ship-owners au extOnsive fundamental inestigation into the

mecha-nism of the corrosive behaviour of pipe system materials was

started therefore.

Since the coppernickel alloys with 10% Ni and 1.5% Fe show an encouraging behaviour the experiments wre concentrated on these alloys.

The investigation is directed to the development of treatment

and design methods aiming at the increase in life-time of the

seawater system without increasing first costs disproportionately In this first report the criteria determining the selection of a material for and the requirements of the seawater system as wel as the various corrosion phenomena are summarized and the in vestigations carried Out are mentioned.

The first fase of the investigations was aimed at the influence of heat treatment and the service conditions on the occurrence and the behaviour of the protective layer.

A fundamental examination of the strUcture of this layer was started.

The conclusions are summarized in chapter 4 Future work is

mentioned in chapter 5.

Sununary

CONTENTS

page

7

1

Infroduction

. . . 7

SOme aspects in the selection of materials for seawaterpipingsystems

. 7

2.1

Economical aspects

. . 7

2.2

Working aspects.

. . . _{. 7}

Corrosion aspects of materials in seawaterpipingsystems in relation

tO life ad corrosion prevention

8

3.1

COrrosion aspects

8

3 1 1

Factors determimng the corrosion resistant properties of

materials

. . . _{. 8}

3 1 2

Factors determining the probability of damage of the layer

8

3 1 3

Corrosion phenomena in seawaterpipingsystems

9

3.L4

COrrosion prevention

. . 10

3.2

Evaluation of materials to be used in sea.waterpipingsystems

10

4

Experimental work

. 12

4.1

Introduction

. . . 12'

4 2

Metallurgical aspects

13

4 3

_{The influence of heat on the structure after fabncation}

14

4.4

The protective layer

. . . - _{. 14}

5

Future work

. 15

6 AcknOwledgement I 16

THE CORROSiON BEHAViOUR OF CUNIFER-10 ALLOYS

IN SEAWATERPIPINGSYSTEMS ON BOARD SHIP

PART I

by

Ir W. J. J. GOETZEE

and

Dr. Ir. F. J. KIEVITS

Summary

After a general and short survey concerning the selection Of materials to be used fOr seawaterpipingsysterns on board ship with respect to the specific environmental conditions and the various corrosion aspects the first results of a thorough study of the corrosion behaviour of Cunifer-lO alloys are described.

The mfluence of the heattreatment on the corrosion behaviour of the alloy and the influence of the operating conditions on the

protective 1yer are discussed.

Finally proposals are made for future work.

1 Thtrodtiction

These exprithents were started to improve the

reliabi-lity of seawaterpipingsystems on board ships. A

re-search program was set up tO evaluate the. materials

used in these systems. As the coppernickel alloys with

10% Ni and 1.5% Fe showed a promising behaviour

the experiments were concentrated on these alloys. As

not much experience was available in Holland in the

field of seawater corrosion, the problem was attacked

from various sides. It is hoped, that with this approach

and the results, it can be proved that more research

will be necessary on the subject "corrosion in marine

engineering"..

This report summarises the first results that have been

achieved. Theoretical considerations have, in generals

been avoided.

The specific research reports can be fOund in the

literature reference.

This report is devided into four chapters. In chapter

2 the selection criteria of materials of

seawaterpiping-systems are discussed.

Chapter 3 deals with requirements of these materials

in the system

The experiments and results are described in chapter

4.

Future work is discussed in chapter 5.

2 Some aspects in the selection of materiJs for

sea-waterpipingsystems

There are two different groups:

Economical aspects.

Working aspects.

2.1

Economical aspects [I]

Often the selection of a material for a seawaterpiping

system is only determined by an economic calcülãtion

Since we consider a seawaterpipingsystem as bein

a part of the ship, we must also calculate the ecoftomi

role of the pipingsystem within the scope of the econo

my of the ship as a whole. The profitearning capacit

of a material applied in seawaterpipingsystems will b

deterthined by the following factors:

I.

Capital investment.

Life of the pipe.

Life of the ship.

Labour costs for replacement and installation.

Repair and paiflt costs.

Weight savings by application of lighter materials

which results in lower power required to haUl a

given payload.

The reliability of the system, determining the costs

of unscheduled "out of service" time.

We refer to "Economic considerations in the

selec-tion of materials for marine applicaselec-tions" for a

com-paring economic calculation of six materials [I]. In

this paper it is calculated, that the highest

profitearn-ing capacity can be expected from the metal alloy

cupro-nickel-lO and the plastic PVC. It also becomes quite

clear, that the life of the pipematerial is a very

impor-tant factor and is fully determined by the corrosion

behaviour of the material under the circumstances,

which are characteristic for exploitation on board ships.

In chapter 3 we will return to this subject.

2.2

Working aspects

In some cases an economic evaluation is not decisive

g c

V

8

fOr the selection of a certain material. Examples of

these are found in Navies, since the task of a naval ship

is different from that of a merchant vessel.

Example A

In the case of minesweepers the problem is to combine

reliability of the material with antimagnetic properties.

In some cases this has led to serious trouble.

Example B

The application of plastics in seawaterpipingsystems

has many disadvantages because of its changing

prop-erties at higher temperatures as for example:

Bad fire resistance.

Development of toxic fumes.

3

Weakening of the pipebonds at moderate high tem

peratures.

In general it can be said, that when the reliability of a

material is low at high temperatures, the application

in coolingwaterpipingsystems is not acceptable.

Im-provement of the heatresistent properties of plastics

will enormously increase its possibilities.

3

Corrosion aspects of materials in

seawaterpiping-systems in Eelation to life and corrosion prevention

At present seawaterpipingsystems operate under the

following circumstances:

I. Minimum nominal water velocity of 3 rn/sec.

2.

Agressive and poluted environment.

Bad workmanship of the system in ships.

Bad design of the system.

Bad heattreatment of the material during

construc-tion of the system.

Maxiniuin temperature of 50 °C.

3.1

Corrosion aspects

3.1 .1

Factors determining the corrosionresistant

pro-perties of materials

Corrosion of metals is an affection of material which

mostly is not economical acceptable. There are however

some metalalloys, which are capable of building up a

protective layer or film on the metal surface, the metal

being protected against further corrosion. It is clear,

that only these type of metalalloys are to be considered

for application in seawaterpipingsystems.

The protective layer is the result of interaction

between the environment (seawater) and the material

(metalalloy).

Good protection of the metal is possible when the

layer meets certain requirements, such as:

1. Not porous.

Good sticking.

Wearproof.

Seifrepairing.

Anti-fouling.

These properties are directly determined by.:

Composition and structure of the metallaloy.

Composition of the environment.

Temperature.

3.1.2

Factors determining the probability of damage

of the layer

The protective properties of the layer can be affected

in three ways:

By changing the structure of the layer in a negative

sence.

By mechanical wear of the layer.

By galvanic mechanisms

When the composition of the environment

changes, it is possible that the layer will disappear and

that another layer with a bad structure will grow on the

metal surface. Higher temperatures also have influence

on the interaction mechanism between environment

and material with the result that the growing layer is

not wearproof and goodsticking.

Mechanical wear is nucleated from the

environ-ment in the pipe. Some parameters are listed be1o'w:

The seawater velocity.

At higher velocities the wear

of the layer will increase.

The air-content of the seawater..

Locally in the

pipingsystem high velocities can be generated fo1

lowed by pressure reduction. The dissolved air will

be immersed as bubbles giving opportunity to the

water to impinge through the bubbles on the rnetal

surface These forces are considerably higher than

without airbubbles because of the fact that the

water during its movement through the bubbles to

the metalsurfâce is hardly slackened. This impulsel

gain is now transferred to the layer and

consequent-ly increases the probability of damaging this layer.

The temperature.

This factor is also important

in relation to mechanical damage on account of

two aspects:

a

The solubility of air in seawater decteases with

higher temperatures.

I

b. At higher temperatures the probability of getting

boiling phenomena is increasing at places in the

system where turbulence is generated. The for

mation of a vapourbubble is mostly followed by

an implosion by which pressures in the order of

1000 atmospheres are very common

When a vapour bubble implodes on the layer,:

ad 3.

In some circumstances it is possible, that the

layer cannot grow locally in the system:

I. By sedimentation of particles on the metalsurface.

These particles can be originated:

from polluted seawater (much sand and algae).

from the heat treatment after bending by which

coalparticles are generated from organic filling

materials.

from unprofessional welding (welding drops

left behind on the metalsurface).

By coupling with more precious metals.

In both case 1. and 2. places where the layer cannot

grow have a tendency of going in solution anodically

and thus strongly restricting the life of the material.

Moreover it is possible that on the metalsurface

itself strong anodic places (structure and stress

dif-ferences) are located, which are also doomed to

dissolve.

3.1.3

Corrosionphenomena in seawaterpipingsystems

Galvanic corrosion (see 3.1.2 ad 3 points 2 and 3).

Examples: A. Coupling of steel

with copper.

Here the steel is affected generally (galvanic

cor-rosion on a macro-scale). B. Dezincification (fig. 1),

of some non-inhibited brassalloys. (galvanic

corro-sion on a micro-scale.)

Pit corrosion (See 3.1.2 ad 3-1).

Here the corrosion

rate is locally very high and sudden leakage of the

pipe is very probable. Pitting corrosion is also

gal-vanic corrosion on a micro-scale.

Stress-corrosion (See 3.1.2 ad 3-3). Residual

stress-es in material after cold bending can initiate this

type of corrosion (fig. 2).

Impingement attack (See 3.1.2 ad 2-2 and 3a).

This

type of corrosion shows often horse shoe shaped

affections with the toe in the direction of the flow.

The corrosionrate can be seriously high (fig. 3).

Fig. 2. Stress corrosion of an austenitic (Cr, Mn) steel. Sliplines in the crystals are attacked.

Fig. 3. Impingement attack of a cunifer-5 seawaterpipe.

Cavitation-corrosion. (See 3.1.2 ad 2-3b).

At places

where local turbulence is generated at sharp bends,

misaligned flanges, partly opened valves etc. this

type of corrosion is very likely to occur. This is a

very serious affection because of the destructive

character of cavitation.

Sulfur corrosion.

The presence of anaërobe

sul-phate bacteria in stagnant seawater stimulates the

formation of a sulphide film. This film is very

porous and bad sticking, consequently the

cor-rosionrate is high under these circumstances.

Materials with good resistance to pit- and

galvanic-corrosion, impingement attack and cavitation

cor-rosion in seawaterpipingsystems on board ships should

Fig. 1. Dezincification of a Cu 60 Zn 40 plug inserted

be considered as economically acceptable for

applica-in a cunifer-5 seawaterpipapplica-ingsystem.

tion in these systems.

10

Table I. Methods to prevent corrosion

From this table it is evident that a proper layout, good pipe manufacturing methods and a proper heattreatment of the material during construction are the basic means for a successful corrosion prevention.

3.1.4

Corrosion prevention

In the preceding table (table I) some corrosion

preven-tion methods are listed which should be applied to

attack a certain type of corrosion.

3.2

Evaluation of materials to be used in

seawater-pipingsystems

Red copper. [2].

This metal is at present practically

only used as a material for sanitary piping. In

sea-water it is very sensitive to impingement attack.

Admiralty brass [2] (71 Cu, 28 Zn, 1 Sn).

This is

a one phase alloy, but suffers deñncification because

of segregation in the structure, when the alloy is not

inhibited with 0.O02-0.05% arsenicum. It is

moder-ately resistent to impingement attack.

Alluminium brass [2] (77 Cu, 21 Zn, 2 Al±As).

The addition of aluminium in this alloy generates a

stronger layer on the metalsurface in seawater.. The

material is relatively cheap but it is very sensitive

to bad heattreatment and transformation, so that

often the construction of the pipingsystem is done

in the pipe factory itself. A smooth installation of

the system in the ship is quite impossible in this way.

(a + j9) brass [2] (6O Cu, 40 Zn).

This alloy suffers

dezincification when no measures are taken. Coating

and cathodic protection are two of these measures

of which the latter has the disadvantage of loosing

the antifouling property characterizing all copper

alloys. In addition this alloy is very sensitive to

stress-corrosion.

Steel.

Here we distinguish:

Galvanized steel, which is moderately

satisfac-tory.

Ebonitized steel, which is very corrosion

resis-tant but very sensitive to vibration of the ship

Rubberlined steel, is satisfactory, provided that

the lining is done under special working

condi-tions.

6..

Cupro-ñickel alloys [3] [4].

Here we have:

Cunifer-30 (30 Ni, 0.5 Fe, 03 Mn, rest Cu)

Cunifer-lO (10 Ni, 1.0 Fe, 0.6 Mn, rest Cu)

Cunifer- 5 (5 Ni, 1.2 Fe, 0.6 Mn, rest Cu)

In order to understand the position of the cupro nickel

alloys with respect to the corrosionresistance in

sea-water of some alloys already discussed, we have chosen

the next three types of corrosion, which are

represen-tative for the corrosion problems in seawater:

Galvanic corrosion.

Impingement attack.

Cavitation corrosion.

I. Galvanic corrosiOn [3] [4].

In designing a

piping-system it is very difficult to avoid-coupling materials

of different electrochemical behaviour.

Heatexchangers as well as valves are often not made

of the same material as the pipe itself. Therefore a

thorough study of the galvanic corrosion aspects is very

important. The following table (table 2) gives informa-.

tions about the direction of the galvanic current when

two metals of different electrochemical. properties are

coupled.

In the table the electrocheniical potentials of alloys'

versus a saturated calornel electrode in flowing

sea-water are listed.

In a given galvanic couple the more electronegative'

metal will go in solution anodically, while the more

electropositive metal will only be slightly affected. The

difference in electrochemical potential is no ctitrion

for the corrosionrate of the anodic material. As soon

as the current is initiated, polarisation phenomena'

occur on both cathode and anode.

Type of corrosion Prevention method Better "outlay" No stresses and proper alignment Proper pipe- manu-factunng methods Proper heattreat-ment during construction of the system Low nominal water velocity Low temp. High air content Cathodic protection or sacrifice electrodes No coupling of material

with V>

100 mV No turbulence generating appendages in the system High pressure 1. Galvanic corr.

2.Pitcorr.

3. Stress corn 4. Impingement attack 5. Cavitation corr. x -x x x x x x x x x x x x x x x x x x x x x x x x x x x

Table 2. Nominal seawater velocity 4 rn/sec. except for nickel 2.3 rn/sec * [4)

The practice in seawater has shown, that the anodic

polarisation is only small so that the corrosionrate is

determined for the greater part by the degree of

polar-isation of the cathode metal. For this reason one is

confronted in the first instance with the paradoxical

situation, that coupling of cunifer-lO with cast-iron

valves causes less galvanic corrosion than copper.

A second aspect which must be kept in mind is the

metal surface ratio of the anodic metal with respect to

the cathodic metal. If this ratio is small, the corrosion

rate of the. anodic metal will be relatively high.

Returning it is evident, that the table gives no

infor-mation about the corrosionrate of a certain metal but

is restricted to give an idea of the galvanic function

(cathode or anode) of a metal in a given galvanic couple.

It is shown from this table, that the cupro-nickels

have relatively high nobility and in practice it is found,

that the cathodic polarisation characteristics of the

cupro-nickels are better than those of copper and other

alloys.

2. Impingement attack [2,

[3], [4].

The maximum

acceptable nominal seawaterveloôity is a good measure

Table 3. Maximum acceptable nomihal water velocities for sev-eral metals/alloys

Parameters: 3 vol % air Temperature 20 °C Clean seawater

for the sensitivity of a metal for this type of corrosion.

In table 3 these velocities are listed for eight metals

and alloys.

The data have been obtained from

BNFMRA (British Non Ferrous Metals Research

Association) jet tests.

These data should be handled with care since in

practice there are circumstances which can lead to a

lower maximum water velocity such as:

Bad "outlay" (local turbulence).

Small pipe diameter (Small allowance).

Higher air content of the seawater.

Pollution of the seawater.

Higher temperatures of the seawater.

The probability of premature failure of some metals

and alloys by impingement attack versus the nominal

seawater velocity in a pipe is reproduced in fig. 4 4].

Copper adm1iralty A brass aluminium. brass

/70 30

/"iCu

pro-nickel 1

/

/

9010

cu-ni-fe

Fig. 4. Possibility of occurrence of impingement attack in sea-water

The cupro-nickels have also with respect to the

cor-rosion ecor-rosion behaviour relatively favourable

quali-ties. Cunifer-5 however doesn't. follow the good

be-haviour of cunifer-lO and cunifer30 in practice because

of its sensitivity to bad heattreatment and bad outlay.

3. Cavitation-corrosion.

These tests were caned out

in an apparatus in which seawater velocities of 35-45

rn/sec were generated.

In table 4 the corrosionrate is listed as a function of

velocity and temperature [4].

It is obvious from these results, that the temperature

has a distinct effect on the resistance of cupro-nickel

70/30 (0.5% Fe) and carbon -steel to cavitation-erosion.

Cupro-nickel 90/10 is relatively good resistant; This

statement is also proved by experiments (fig. 5) at lower

seawater velocities to a maximum of 25 ft/sec. (8.5

m/sec) with the Rotating Disc Corrosion Apparatus

[3].. Metal/alloy Tempeiature Volts versus sat. cal. electrode Zinc 26

-1.03

Mild steel 24

-0.61

Copper 24

-0.36

Admiralty brass 24.6

-0.36

Admiralty bi-ass 11.9

-0.30

Aluminium brass 24.6

-0.29

90/10 Cu-Ni (1.4% Fe) 17.0

-0.29

90/lOCu-Ni(l.4%Fe) 6.0

-0.24

70/30 Cu-Ni (0.5 1% Fe) 17.0

-0.24

70/30 CuNi (0.51% Fe) 6.0

-0.22

Nickel 25.0 -0.10 * Titanium 27.0

-0.10

Metal/alloy Max. norn. -seaw. velocity (m/sec) Cunifer-30 4. Cunifer-lO 4 A1urhiuth brass 2.6 Cunifer-5 1.8 Admiralty brass 1.4 Galvaniied steel 1.2 Red copper 1.0 (a-}-) brass 1.0 2 3 nominal water 6

.5

4 velocity, m!sec

12

25

0

Table 4. Corrosion rates of different metals/alloys as a function of temperature and seawater velocity.

Resuming we can say that cunifer-lO is most

appro-priate for use in seawaterpipingsystems for three

rea-Sons:

admiralty

copper nickel, low iron

0.05% Fe

Copper Nickel, high iron 0.4 % Fe

10 % Copper

Nickel 0.7 % Fe 10 15 20 25 30 velocity(FPS)

Fig. 5. Effect of velocity on depth of attack in seawater. Fig. 6b. Photo of the system. Ferry to Texel in background.

seawater piping system

1110 :.:.

F.R.C.

=

XB.V.

=

pressure safety valve

r

electro-motor pump seaweed case quayside B.V. FR. 0 T.R. 5.v. Code Data

S.V. = Slide Valve Electromotor: > 5 hp

B.V. = Ball Valve Pump in serging point:

F.V. = Foot Valve = 5. JØ3 m3/sec. - zIp 6.25 atm.

F.R. = Flow Recorder

0 Pipe =6.6cm

T.R. = Temp. Recorder

F.R.C. = Flow Recorder Control

P = Pressure measurement

Rb=3or4xØ pipe= ±23cm

I. A favourable economic evaluation thanks to:

High corrosion resistance and therefore long

life;

High reliability.

Good experiences abroad.

Good antifouling properties.

4

Experimental work

4.1

Introduction

To examine the corrosion behaviour of cunifer-lO

under several conditions a corrosioncircuit was built

at the Naval base in Den Helder. The outlay of the

pipingsystems is shown in fig. 6a.

'

'IL'

ilL

'ii

Materials Cunifer-lO Testsection Fiberglass P.V.C. cavitation section

Fig. 6a. Outlay of the seawaterpipingsystem in the harbour of Den Helder. Material Temper-ature ('C) . Velocity (m/sec) Corro-sionrate (mm/year) Nickel 200 27 40.2 12.7 Monel 400 11 43.0 10.2 Monelk500 11 43.0 10.2 Cupro-nickel 70/30 (0.5% Fe) 11 43.0 1219 Cupro-nickel 70/30 (0.5% Fe) 17 41.8 1372 Cupro-nickel 70/30 (0.5% Fe) 24 41.5 1397 Cupro-nickel 70/30 (0.5% Fe) 26 35.7 1930 Cupro-nickel 70/30 (5% Fe) 28 35.7 178 Cupro-nickel 90/10(1.5% Fe) 18 42.1 864 Steel 10 43.3 3048 Steel 17 41.8 4572 Steel 27 40.5 7874

00

00- '00-)00 )00

o0.

0 0 4110

A research program was set up and the following

points were investigated:

The influence of heattreatment on the corrosion

behaviour of the alloy.

The influence of operating conditions on the

pro-tective layer of the alloy.

At the same time a fundamental study of the

pre-cipitated structure and the protective layer was started.

Several samples (in the condition after manufacturing

or specially heat-treated) were subjected to fresh and

polluted seawater.

Potential measurements on board of ships were

carried out to study the formation of the protective

layer.

In the following chapters the results of the

experi-ments (until april 1968) will, after a metallurgical

in-troduction, be summarised.

4.2

Metallurgical aspects of cunjfer-1O

The protective layer of a metal will be greatly

influen-ced by the metal underneath it. The most favourable

condition will be offered if a one-phase structure is

present. As the cunifer-lO alloy is a two phase a+/9

structure (fig. 7a) a one-phase structure can be obtained

by heating the alloy in the a region of the phase

dia-gram followed by a quench.

As this is a metastable situation a potential danger

of a precipitating

/9

phase will always be present.

The precipitation of this

_fi

fase will be accelerated if

the alloy is heated in the a + /9 region, which can occur

in practice during welding and hot-bending of the pipes

(fig. 7b).

A program has therefore been started where

sam-ples were heated and the structure after heating was

examined.

With the electron microscope, X-ray microanalysis

and X-ray diffraction the structure of the

/9

phase was

examined. [6] It was found, that the precipitating phase

was a face centered cubic structure with a composition

1.5 % Fe

1234

% Fe

structure after

quenching

Fig. 7a. Phase diagram of

CuNi 10Fe.

+

/3 ingrain +/3 ingrain boundaries p.

stucture after

heating in

+/3

region

time

Fig. 7b. Precipitation of the /3 phase ofaCuNilOFe 1.5 alloy after heating in the

_a+fl

region.

of l7°/ Fe and 31% Ni. The consequence of this

com-position on the formation of the protective layer is a

selective corrosion.

To investigate the existence of the a phase in a

com-mercial alloy after fabrication, a structural research of

cunifer-lO pipes from several manufacturers was made.

A typical structure of these pipes is shown in fig. 8.

900

800

700 600 500 400 300 200 100

---

-...-i

--

-:2--.

-.-,---Fig. 8. Structure of a commercial cunifer-lO.

With X-ray microanalysis it was found that heavy

seg-regation of Ni and Fe is present in this alloy. The

percentages of two extreme conditions were [7]:

This is important as a lower Ni and Fe content, will

enhance corrosion if the protective layer is damaged.

No /9-precipitation was found in the grains.

Precipi-tation in the grain boundaries was not investigated.

However in previous examinations (unpublished reports

AC

solubility-limit of the /9fase

- B D

no/I fase /3fase precipitated

-

-1

5 10 15. 20

times (minutes)

Fig.9. T.T.T.diagram of cunifer-lO constructed from hardness measurements. Precipitationof /3 willoccur if the a+fl regionis

crossed during hot bending or welding. (CD). Measurements of the electrical resistance indicate that the a+/I

region will be closer to the temperature axis. (arrows)

Ni Fe

Mn

Cu

(percentages)

13.5 2.40 0.7 83.4

14

900

800

700

600

500

400

300

200

100

Royal Netherlands Navy) precipitation of the

phase

was detected in:the grain boundaries in curiifer-5 alloys.

It is therefore expected that the

phase will be present

too in cunifer-lO alloys.

4.3

The influence of heat on the structure after

fabri-cation

The influence of heat on the precipitation of the

phase

can be well understood with a I.T.T.

(transformation-time-temperature) diagram. Therefore a TT.T. diagram

of cunifer-lO was constructed (fig. 9). To cOnstruct

this diagram the hardness was measured at various

temperatures and times [6]. If during hot bending or

welding the a ±

j9

region is crossed (CD) precipitation

of

9 will occur.

As the change of the hardness is a rough estimate of

the precipitationprocess the change of the electrical

resistance of cunifer-lO wires was measured at the same

time [8].

From these experiments it could be concluded that

the a +

_fi

region will be close to the temperature axis

(arrows in fig. 9). Therefore cooling from high

temper-atures will be more critical if precipitation of the

phase

must be avOided (line AB fig: 9). A further refinement

of the diagram is still in progress.

To study how welding might effect the structure of

cuniferl0 pipes, experiments were done in the welding

laboatOry of Prof. Dr.

r. H. G. Geerlings (Technolo

gical University Delft). Two pipes.were rotated with

constant Speed and welded With cunifer-5 (argon-arc)J

The temperature at several distances of the weld wa

measured with thermo-couples. In fig. 10 the change

oltemperature with time at several distances from th

weld is given [9]. As can be seen from this and the

previous figure cooling speeds close to the weld will

be rather critical for precipitation. As welding in thi

case is performed under closely controlled conthtions

it

is expected that precipitation will occur during

welding in practice. Investigations into this are still in

progress.

A typical welding structure is given in fig. 11. It was

found with micro hardness measurements that in the

transformation zone a hardness increase was present

[9].

4.4

The protective layer

As no experience with protective layers of cunifer-l0

was available, samples (in the as fabricated condition;

and precipitated) were oxjdized in air and the structure;

of the oxide layer with several techniques investigated.

0.25

0.5

0.75

1.0

1.25 1.5 1.75

2.0

2.25

25

2.75 3.0 3.25

,.. t/tcl

Fig. 10. Welding experithents on cunifer-lO pipes. Change of temperature with time at several distances from the weld.

Fig. 11. Typical welding structure of a cunifer-lO pipe welded

with cunifer-5 (argon arc). Between the weld (on the left) and

the tube a transformation zone is visible.

The samples were then immersed in seawater and

pol-luted water. From these experiments it could be

con-cluded that [10]:

the oxide of cunifer-lO consisted of an outer layer

d.

of brittle Cu20 and an innerzone of internal oxides

of iron, nickel and manganese.

The corrosion in stagnant seawater is influenced by

the oxide and the precipitation. At longer immersion

e.

crystal orientation determines attack by pitting

corrosion.

Further studies on the formation of the protective layer

are still in progress, in practice and on board ships.

f.

These results will be published in the next report.

5

Future work

1. Macro corrosion lestcircuit

In this circuit a ventury tube (fig. 12) will be

install-ed in order to generate high velocities. In the throat

of the ventury there is a plugconstruction with

which small metal bars can be clasped. We intend

to get quantitative information about the cavitation

resistance of cunifer-lO at varying velocities of the

seawater and moreover to explain this behaviour

theoretically by means of fundamental research

(velocity > 15 m/sec).

Furthermore velocities higher than 4 rn/sec and less

than 15 rn/sec. will be generated in the circuit in

order to trace the resistance against

corrosion-erosion, especially with respect to flow disturbances

by installation faults and appendages in the system.

A sample apparatus (fig. 13) is to be installed in the

circuit in which metal samples have been clasped

and in which the flow from a hydrodynamic point

of view is identical to the flow through pipes.

Fig. 12. Ventury tube to be used

for experiments at high speed.

At the moment soldering and welding connections

have been fitted in the circuit. For some months

the corrosion resistance will be checked at a

nom-inal seawatervelocity of 3 rn/sec.

Potential measurements on board ships will be

repeated in this circuit with variable water

compo-sition in order to understand the course of the

elec-trochemical potential of these practical

measure-ments.

A titanium pipe (fig. 14) will also be installed to start

the material research on this metal and its alloys

especially with relation to its application in

heat-exchangers.

Fig. 13. Apparatus for installation of several test pieces in the

16

Fig. 14. Tubewithflangesmade of titanium. This tube is coupled to the other pipes in the piping-system.

Micro corrosion tesicircuit

In this circuit on laboratory scale it is possible to

vary the aircontent and the temperature of the

flowing seawater. Furthermore the potentiostatic

characteristics of cunifer- 10 in flowing seawater will

be measured in this circuit.

Fundamental research will be continued in trying

to understand the practical corrosion phenomena

from the theory.

6 Acknowledgement

The Netherlands Ship Research Centre TNO

acknowl-edges gratefully the cooperation of the Royal

Nether-- lands Navy and the Royal Netherlands Steamship

Company which considerably facilitated the work

re-ported.

References

I. LAQUE, F. L. and A. M. TuTmu.., 1961, Transactions S.N.A.M.E., Vol. 69 p. 619. "Economic considerations in the selection of materials for marine application". CARSON, J. A. M., March 1963, Journal of the Royal Naval

Scientific Service, 3, p. 98. "The corrosion of copper and its alloys in naval ships".

STEWART, W. C. and F. L. LAQUE, 1952, Corrosion, 8, p. 259. "Corrosion resisting characteristics of iron modified 90: 10 cupro-nickel alloy".

MAY, T. P. and WELDON B. A., 1964, International nickel. "Copper nickel alloys for service in seawater".

Srisv, G. P. and P. T. GILBERT, Discussion ref. 4. Bano, P. J. and R. G. DE LANGE, 1966, Progress report

M66-933, Metals Research Institute TNO, Delit. "Cunifer

alloys" (in Dutch).

BERG, P. J. and R. G. DE LANGE, 1967, Progress report

M67-711, Metals Research Institute TNO, Delft. "Cuniler

alloys" (in Dutch).

PLATERINK, G. R. and A. J. BROUWER, October 1967, Report physical laboratory Royal Naval College (Den Helder). "Measurements of the electrical resistance of cunifer-lO" (in Dutch).

GOETZEE, W. J. J., Report 1967-2, Royal Naval College (Den Helder). "Welding Experiments of cunifer-lO" (in Dutch). Bcao, P. J., F. J. KiEvn's and R. G. DE LANGE, 20th to 24th September 1968, Paper second International Congress on Marine corrosion and fouling, Athens, Greece.

PRICE PER COPY DFL 10.- M = engineering department_{S = shipbuildmg department}

C = corrosion and antifouling department

Reports

1 S The determination of the natural frequencies of ship vibrations (Dti1ch). H. E. Jaeger, 1950.

37 M Propeller excited vibratory forces in the shaft of a sing1 screw

tanker. 3. D. van Manen and R. Wereldsma, 1960. 3 S Practical possibilities of constructional applications of aluminium

alloys to ship construction. H. E. Jaeger, 1951.

38 S Beamknees and other bracketed connections. H. E. Jaeger and J. J. W. Nibbering, 1961.

4 S Corrugation of bottom shell plating in ships with all-welded or partially welded bottoms (Dutch). H. E. Jaeger and H. A.

Ver-39 M Crankshaft coupled free torsional-axial vibrations of a ship's

propulsion system. D. van Dort and N. J. Visser, 1963. beek, 1951. 40 S On the longitudinal reduction factor for the added mass of

vi-5 S Standard-recommendations for measured mile and endurance trials of seagoing ships (Dutch). J. W. Bonebakker, W. J. Muller

brating ships with rectangular cross-section. W. P. A. Joosen and J. A. Sparenberg, 1961.

and E. J. Diehl, 1952. 41 S Stresses in flat propeller blade models determined by the moire-6 S Some tests on stayed and unstayed masts and a comparison of method. F. K. Ligtenberg, 1962.

experimental results and calculated stresses (Dutch). A. Verduin and B. Burghgraef, 1952.

42 5 Application of modern digital computers in navalarchitecture. H. 3. Zunderdorp, 1962.

7 M Cylinder wear in marine diesel engines (Dutch). H. Visser; 1952. 43 C Raft trials and ships' trials with some underwater paint systems.

8 M Analysis and testing of lubricating oils (Dutch). R. N. M. A. P. de Wolf and A. M. van Londen, 1962.

Malotaux and J. G. Smit, 1953. 44 S Some acoustical properties of ships with respect to noise control. 9 S Stability experiments on models of Dutch and French standard- Part. I. 3. H. Janssen, 1962.

ized lifeboats. H. E. Jaeger, J. W. Bonebakker and J. Pereboom, in collaboration with A. Audigé 1952.

45 5 Some acoustical properties of ships with respect to noise control. Part II. J. H Janssen, 1962.

lOS On collecting ship service performance data and their analysis. J. W. Bonebakker, 1953.

46 C An investigation into the influence of the method of application

on the behaviour of anti-corrosive paint systems in seawater.

11 M The use of three-phase current for auxiliary purposes (Dutch). A. M. van Londen, 1962.

3. C. G. van Wijk, 1953. 47 C Results of an inquiry into the condition of ships' hulls in relation

12 M Noise and noise abatement in marine engine rooms (Dutch). to fouling and corrosion. H. C. Ekania, A. M. van Londen and

Technisch-Physische Dienst TNO-TH, 1953. P. de Wolf, 1962. 13 M Investigation of cylinder wear in diesel engines by means of

labo-ratory machines (Dutch). H. Visser, 1954.

48 C Investigations into the use of the wheel-abrator for removing

rust and millscale from shipbuilding steel (Dutch). Interim report.

14 M The purification of heavy fuel oil for diesel engines (Dutch). J. Remmelts and L. D. B. van den Burg, 1962.

A. Bremer, 1953. 49 S Distribution of damping and added mass along the length of a

15 S Investigations Of the stress distribution in corrugated bullcheads shipmodel. 3. Gerritsma and W. Beukelman, 1963. with vertical troughs. H. E. Jaeger, B. Burghgraef and I. van der

Ham, 1954.

50 S The influence of a bulbous bow on the motions and the propul-sion in longitudinal Waves. J. Gerritsma and W. Beukelmanl963. 16 M Analysis and testing of lubricating oils H (Dutch). R. N. M. A.

Malotaux and 3. B.. Zabel, 1956.

51 M Stress measurements on a propeller blade of a 42,000 ton tanker on full scale. R. Wereldsma, 1964.

17 M The application of new physical methods in the examination of lubricating oils. R. N. M. A. Malotaux and F. van Zeggeren,1957.

52 C Comparative investigations on the surface preparation of

ship-building steel by using wheel-abrators and the application of shop-18 M Considerations on the application of three phase current on board coats. H. C. Ekama, A. M. van Londen and 3. Remmelts,, 1963.

ships for auxiliary purposes especially with regard to fault pro- 53 S The braking of large vessels. H. E. Jaeger, 1963. tection, with a survey of winch drives recently applied on board

of these ships and their influence on the generating capacity

(Dutch). J. C. G. van Wijk, 1957.

54 C A study of ship bottom paints in particular pertaining to the

behaviour and action of anti-fouling paints A. M. van Londen,

1963.

19 M Crankcase explosions (Dutch). J. H. Minkhorst, 1957. 55 S Fatigue of ship structures. J. J. W. Nibbering, 1963. 20 S An analysis of the application of aluminium alloys in ships'

structures. Suggestions about the riveting between steel and

56 C The possibilities of exposure of anti-fouling paints in Curaçao,

Dutch Lesser Antilles, P. de Wolf and M. Meuter-Schriel, 1963. aluminium alloy ships' structures. H. E. Jaeger, 1955. 57 M Determination of the dynamic properties and propeller excited 21 S On stress calculations in helicoidal shells and propeller blades.

3. W. Cohen, 1955.

vibrations of a special ship stern arrangement. R. Wereldsma, 1964.

22S Some notes on the calculation of pitching and heaving in longi-tudinal waves. J. Gerritsma, 1955.

58 S Numerical calculation of vertical hull 'vibrations of ships by

discretizig the vibration system. J. de Vries, 1964. 23 S Second series of stability experiments on models of lifeboats. B.

Burghgraef, 1956.

59 M Controllable pitch propellers, their suitability and economy for large sea-going ships propelled by conventional, directly coupled

24 M Outside corrosion of and slagformation on tubes in oil-fired engines. C. Kapsenbérg, 1964.

boilers (Dutch). W. J. Taat, 1957. 60 S Natural frequencies of free vertical ship vibrations. C. B. Vreug-25 S Experimental determination of damping, added mass and added denhil, 1964.

mass moment of inertia of a shipmodel. J. Gerritsma, 1957. 61 S The distribution of the hydrodynamic forces on a heaving and 26 M Noise measurements and noise reduction in ships. G. J. van Os

and B. van Steenbrugge, 1957.

pitchingshipmodel in still water. 3. Gerritsma and W. Beukelman,

1964.

27 S Initial metacentric height of small seagoing ships and the in-accuracy and unreliability of calculated curves of righting levers.

62 C The mode of action of anti-fouling paints: Interaction between

anti-fouling paints and sea water. A. M. van Londen, 1964. 3. W. Bonebakker, 1957. 63 M Corrosion iii exhaust driven turbochargers on marine diesel 28 M Influence of piston temperature on piston fouling and pistonring

wear in diesel engines using residual fuels. H. Visser, 1959.

engines using heavy fuels. R. W. Stuart Michell and V. A. Ogale,

1965.

29 M The influence of hysteresis on the value of the modulus of rigid-ity of steel. A. Hoppe and A. M. Hens, 1959.

64 C Barnacle fouling on aged anti-fouling paints; a survey of pertinent literature and some recent observations. P. de Wolf, 1964. 30 S An experimental analysis of shipmotions in longitudinal regular

waves. J. Gerritsma, 1958.

65 S The lateral damping and added mass of a horizontally oscillating shipmodel. G. van Leeuwen, 1964.

31 M Model tests concerning damping coefficient and the increase in the moment of inertia due to entrained water of ship's propellers.

66S Investigations into the strenght of ships' derricks. Part I. F. X. P. Soejadi, 1965.

N. J. Visser, 1960. 67 S Heat-transfer in cargotRnkc of a 50,000 DWT tanker. D. 3. van 32 S The effect of a keel on the rolling characteristics of a ship. der Heeden and L L. Mulder, 1965.

3. Gerritsma, 1959. 68 M Guide to the application of Method for calculation of cylinder 33 M The application of new physical methods in the examination of liner temperatures in diesel engines. H. W. van Tijen, 1965.

lubricating oils (Contin. of report 17 M). R. N. M. A. Malotaux and F. van Zeggeren, 1960.

69 M Stress measurements on a propeller model for a 42,000 DWT

tanker. R. Wereldsma, 1965.

34 S Acoustical principles in ship design. J. H. Janssen, 1959. 70 M Experiments on vibrating propeller models. R. Wereldsma, 1965. 35 S Shipmotions in longitudinal waves. J. Gerritsma, 1960. 71 S Research on bulbous bow ships. Part H. A. Still water perfor-36S Experimental determination of bending moments for three mod

els of different fullness in regular waves. J. Ch. de Does, 1960.

mance of a 24,000 DWT bulkcarrier with a large bulbous bow. W. P. A. van Lammeren and 3. 3. Muntjewerf, 1965.

72 S Research on bulbous bow ships. Part. ll.B. Behaviour of a

24,000 DWT bulkcarrier with a large bulbous bow in a seaway. W. P. A. van Lamrneren and F. V. A. Pangalila, 1965. 73 S Stress and strain distribution in a vertically corrugated bulkhead.

H. E. Jaeger and P. A. van Katwijk, 1965.

74 S Research on bulbous bow ships. Part. l.A. Still water investiga-tions into bulbous bow forms for a fast cargo liner. W. P. A. van Lan,meren and R. Wahab, 1965.

75 S Hull vibrations of the cargo-passenger motor ship "Oranje

Nassau". W. van Horssen, 1965.

76 S Research on bulbous bow ships. Part I.B. The behaviour of a fast cargo liner with a conventional and with a bulbous bow in a sea-way. R. Wahab, 1965.

77 M Comparative shipboard measurements of surface temperatures

and surface corrosion in air cooled and water cooled turbine

outlet casings of exhaust driven marine diesel engine turbochar-gem. R. W. Stuart Mitchell and V. A. Ogaie, 1965.

78 M Stem tube vibration measurements of a cargo ship with special afterbody. R. Wereldsma, 1965.

79 C The pre-treatment of ship plates: A comparative investigation

on some pm-treatment methods in use in the shipbuilding indus-try. A. M. van Londen, 1965.

80 C The pre-treatment of ship plates: A practical investigation into

the influence of different working procedures in over-coating

zinc rich epoxy-resin based pre-construction primers. A. M. van Londen and W. Mulder, 1965.

81 S The performance of IT-tanks as a passive anti-rolling device.

C. Stigter, 1966.

82S Low-cycle fatigue of steel structures. J. J. W. Nibbering and

J. van Lint. 1966.

83 S Roll damping by free surface tanks. J. J. van den Bosch and J. H. Vugts, 1966.

84 S Behaviour of a ship in a seaway. J. Gerritsma, 1966.

85 S Brittle fracture of full scale structures damaged by fatigue. J. J. W. Nibbering, J. van Lint and R. T. van Leèuwen, 1966. 86 M Theoretical evaluation of heat transfer in dry cargo ship's tanks

using thermal oil as a heat transfer medium. D. J. van der Heeden,

1966.

87 S Model experiments on sound transmission from engineroom to accommodation in motorships. J. H. Janssen, 1966.

88 S Pitch and heave with fixed and controlled bowfins. J. H. Vugts,

1966.

89 S Estimation of the natural frequencies of a ship's double bottom by means of asandwich theory. S. Hylarides, 1967.

90 S Computation of pitch and heave motions for arbitrary ship forms. W. E. Smith, 1967.

91 M Corrosion in exhaust driven tUrbochargers on marine diesel en-gines using heavy fuels. R. W. Stuart Mitchell, A. J. M. 5.van Montfoort and V. A. Ogale, 1967.

92 M Residual fuel treatment on board ship. Part II. Comparative

cylinder wear measurements on a laboratory diesel engine using filtered or centrifuged residual fuel. A. de Mooy, M. Verwoest and G. G. van der Meulen, 1967.

93 C Cost relations of the treatments of ship hulls and the fuel con-sumption of ships. H. J. Lageveen-van Kuijk, 1967.

94 C Optimum conditions for blast cleaning of steel plate. J. Remmelts,

1967.

95 M Residual fuel treatment on board ship. Part I. The effect of cen-trifuging, filtering and homogenizing on the unsolubles in residual fuel. M. Verwoest and F. J. Colon, 1967.

96 S Analysis of the modified strip theory for the calculation of ship motions and wave bending moments. J. Gerritsma and W. Beu-kelman, 1967.

97 S On the efficacy of two different roll-damping tanks. J. Bootsma and J. J. van den Bosch, 1967.

98 S Equation of motion coefficients for a pitching and heaving des-troyer model. W. E. Smith, 1967.

99 S The manoeuvrability of ships on a straightcourse. J. P. Hooft,

1967.

100 S Amidships forces and moments on a CB = 0.80 "Series 60"

model in waves from various directions. R. Wahab. 1967. 101 C Optimum conditions for blast cleaning of steel plate. Conclusion.

J. Remmelts. 1967.

102 M The axial stiffness of marine diesel engine crankshafts. Part 1. Comparison between the results of full scale measurements and

those of calculations according to published formulae. N. J.

Visser, 1967.

103 M The axial stiffness of marine diesel engine crankshafts._{Part II.} Theory and results of scale model measurements and comparison with published formulae. C. A. M. van der Linden, 1967. 104 M Marine diesel engine exhaust noise. Part I. A mathematjcalmodeL

J. H. Janssen, 1967.

105 M Marine diesel engine exhaust nOise. Part II. Scale models of exhaust systems. J. Buiten and J. H. Janssen, 1968.

106 M Marine diesel engine exhaust noise. Part. III. Exhaust sound

criteria for bridge wings. J. H. Janssen en J. Buiten. 1967.

107 S Ship vibration analysis by finite element technique. Part. I. General review and application to simple structures, statically loaded. S. Hylarides, 1967.

108 M Marine refrigeration engineering. Part. L Testing of a

decentral-sed refrigerating installatiOn. J. A. Knobbout and R. W. J.

Kouffeld. 1967.

109 S A comparative study on four different passive roll damping tanks. Part I. J. H. Vugts, 1968.

110 S Strain, stress and flexure of two corrugated and one plane

bulk-head subjected to a lateral, distributed load. H. E. Jaeger and

P. A. van Katwijk, 1968.

Ill M Experimental evaluation of heat transfer in a dry-cargo ships'

tank, using thermal oil as a heat transfer medium. D. 1. van der Heeden. 1968.

112S The hydrodynamic coefficients for swaying, heaving and rolling cylinders in a free surface. J. H. Vugts. 1968.

113 M Marine refrigeration engineering. Part II. Some results of testing a decentralised marine refrigerating unit with R 502. J. A. Knob-bout and C. B. Colenbrander, 1968.

116 M Torsionalaxial vibrations of a ship's propulsion system. Part 1. Comparative investigation of calculated and measured torsional-axial

_{vibrations in the shafting of a dry cargo motorship.}

C. A. M. van der Linden, H. H. 't Hart and E. R. Dolfln, 1968. 118 M Stern gear arrangement and electric power generation in ships propelled by controllable pitch propellers. C. Kapsenberg, 1968. 119 M Marine diesel engine exhaust noise. Part IV. Transfer damping

data of 40 modelvariants of a compound resonatorsjjencer.

J. Buiten, M. J. A. M. de Regt and W. P. H. Hanen, 1968.

121 S Proposal for the testing of weld metal from the viewpoint of brittle fracture initiation. W. P. van den Blink and J. J. W.

Nibbering, 1968.

122 M The corrosion behaviour of cunifer-lO alloys in seawaterpiping-systems on board ship. Part I. W. J. J. Goetzee and F. J. Kievits,

1968.

Communications

1 M Report on the use of heavy fuel oil in the tanker "Auricula" of

the Anglo-Saxon Petroleum Company (Dutch). 1950.

2S

_{Ship speeds over the measured mile (Dutch). W. H. C. E. ROsingh,}

195 1.

3 5 _{On voyage logs of sea-going ships and their analysis (Dutch).} J. W. Bonebakker and J. Gdrritsma, 1952.

4 S _{Analysis of model experiments, trial and service performance} data of a single-screw tanker. J. W. Bonebakker, 1954.

5 S _{Determination of the dimensions of panels subjected to water}

pressure only or to a combination of water pressure and edge

compression (Dutch). H. E. Jaeger, 1954.

6 S _{Approximative calculation of the effect of free surfaces on trans.} verse stability (Dutch). L. P. Herfst, 1956.

7 5 _{On the calculatiOn of stresses in a stayed mast. B. Burghgraef,}

1956.

8 S _{Simply supported rectangular plates subjected to the combined}

action of a uniformly distributed lateral load andcompressive forces in the middle plane. B. Burghgraef, 1958.

9 C Review of the investigations into the prevention of corrosion and fouling of ships' hulls (Dutch). H. C Ekarna, 1962.

10 S,M Condensed report of a design study for a 53,000 DWT-class

nuclear powered tanker. Dutch International Team (D.l.T.)

directed by A. M. Fabery de Jonge, 1963.

11 C _{Investigations into the use of some shipbottom paints, based on} scarcely saponifiable vehicles (Dutch). A. M. van Londen and P. de Wolf, 1964.

12 C The pre-treatment of ship plates: The treatment of welded joints

prior to painting (Dutch). A. M. van Londen and W. Mulder, 1965.

13 C Corrosion, ship bottom paints (Dutch). H. C. Ekama, 1966.

14 S _{Human reaction to shipboard vibration, a study of existing} lite-rature (Dutch); W. ten Cate, 1966.

15 M Refrigerated containerized transport (Dutch). J. A. _Knobbout, 1967.

16S _{Measures to prevent sound and vibration annoyance aboard a} seagoing passenger and carferry, fitted out with dieselengines

(Dutch). J. Buiten, J. H. Janssen, H. F. Steenhoek and L._{A. S}

Hageman; 1968.

17 S Guide for the specification, testing and inspection of _glass

reinforced polyester structures in shipbuilding (Dutch). G.Hamm, 1968.