1948-09-23 — Page 8

HALLETT MFG. CO.

THE CHINA MAIL, THURSDAY, SEPTEMBER 23, 1048.

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ENGINEERING PAGE

ALUMINIUM'S USE WITH FOOD IS LIMITED

:

Accordingly, a systematic re- view of the question WIK undertaken in 1930 and a re-

BY CORROSION

*

port was prepared for publica- The importance of aluminium in the food industry tion. This had to be suspend-

ed, however, when the press at

which I was being printed was destinyed early in the war,

No Simple revision seem-- capable of taking the

developments, fully in.... cent

account Panel. the

· op- been

portunity has accordingly, taken to re-wide moal of the original report to include, litera- ture published up to 1946. Thus, an interesting pubbention entitie "Aluminium and aluminium Al- leys the Food Industry. with Special Reference to Corrosion And Its Prevenuor,” WALN pited by J. M. Bryan, Se.. Ph.D. (Low Tersperature Ite-

ร

com-

search Station, Cainbridge), insured as Special Report on Foud investigation. No. 30, by the De- partment of Scientific ond In- dustrial Resench.

The work

represents a

formidable insk. references

the

P

J

has increased steadily.

Many of the earlier troubles arising from the cor- rosion and pitting of aluminium has been large- Jy overcome before the war, but the advantages and the limitations in its uses in connection with food were not fully appreciated.

Non-Capsizable

VIII'IN uspects of 1000000F90 10060

the subject Jeg ring no less than 867. The gund covered In the four secbuis includes: (1)

The metal; (2) corrosion by 1 nepiemus kolutions; (1) corrosion by food products, and (4) me- thods of protection.

Film Weaknesses

The air-tri. l of oxide on the surface of aluminium, now generally recognised as be ing responsible for the corrosion- resisting properties may, accord- ing to various authorities on the subject, possess invitin wenk- nesses and discontinuities due to

structure of the underlying

THE JANAN DEVELOPMENT CORP.theful, and it is likely to be less

Hole Agents For South China

Room 511, China Building, Hong Kong.

40 YEARS EXPERIENCE

IN PROTECTING & WATERPROOFING CONCRETE & STEELWORK

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Sole Agents for Hongkung & China:---

SIBER HEGNER & CO., LTD.

St. George's Building.

W KNO

ENGLAND

Manufacturers of

Contractors' Equipment

known throughout the world.

Tel. 22623,

Sole Agonis:

reliable under immersed condi- Lions on alumia.um alloys than on aluminium itself.

While

work

points and breaks in the natural film are ikely to be the Initial rites of attack (anodic areas), the sub- sequent couI10 of corrosion la Influenced by a number of fac term, including the potential differences arising both from conditions within the metal it. self and from those external to the metal.

Bim win show ferent rlegrers

resistance, under immersed conditions, cording to the nature of the dis- solved substances In solution, their concentrations, the 10- perature, the presence or absence. of oxygen and other factors ex- ternal to the metal.

Healing! of breaks

the Alm

oskle may

In

-30

Fur through wondic polarker- tion. Frequently a decisive fuc-

ES PAR

GREEN DOLPHIN

The Gaskin non-capsizable reversible Ufeboat which is to attempt an Autantie Crossing, arrived recently at Cadogan Plor, London. For over 30 years its inventor, Mr. H. A. Gaa- kin of Knightsbridge, London, has been trying fɔ get the 'Board of Trade to realise the advantages. Experte from the Board salted with her from Kings Lynn, Norfolk, to London to try her out, and It is now anticipated that she wil be adopted.

The 'Green Dolphin,' the non-capsizable Hiroboat, is shown above at Cadogan Pier. Chelasa, London.

of its use as a substitute for the tinplate can.

Ploneer work: on the par-

LIN

- Blbility .of sing aluminium substitut for tinplate was started in Norway during 1914-1918

connection

with fish-canning. The results of pre- liminary tests with aluminium cans coninining Ish were highly encouraging und, while certain dimculties were encountered, these were gradually overcome. The rapid growth in the use of

aluminium cans in Norway an outcome of these developments is indicated by the fact thatho number of cans ured was 2,000,- 000 in 1933, 7,000,000 in 1934. and 12,000,000 in 1935. In gen eral, aluminium commends itself for consideration for food con tainers on account of its physical, !

sanct chemical mechanical

pru- perties.

The metal ionda itself to the engineering operations of bend ing or folding, forming, draw- or pressing and also to the Jesa waual finctures of spion ay and impact aytrusion,

ing

The disadvantages of aluminium, however, are that its strength is lower than that of thined scol of the sate thickness, and this leads to problemi un can-making and processing; also, the finished cans are inuch more Jiabic to buckle or distort during hand- lung.

Aluminium Coatings

The difficulty vunki be elimin- ated if aluminium-conted steel of un alloy of aluminium of ade- quate strength eould be used in place of aluminiu itself for the fabrication of containers,

Vari- pus mechanical processes tinve been devised for cladding or bonding aluminium and alumni- nium alloys to steel, the most Important of whien are the "cold- process developed and rolling" operated by the Trierer Walz- werk A.-G., and the "hot-roll- ing" process, invented by Jor dan and operated on a commer clat scale by the Wickeder Elsen and Stahlwerk G.m.b.H. and luter by the Inesch Ron steel works.

The hot - rolling process 18 carried out ut between 300 und 400 dep. C., using com- paratively low pressures, while for cold-rolling higher pressures are used.

The object of conducting the process. At ordinary tempera- ture or not. above 400 deg. C. is to prevent the formation o any brittle toy layer.

The difficulty of preventing brit- tle layer

when the ma- terial is has also been overcome by using a special type of steel and modifying the com-

tor in passivity or corrosion is the of cathodically formed alkali, as cording to one authority, to the position of the aluminium, so us nature and tubility of the suggested by one investigator. | alkalinity of rome waters,

to permit annealing to be carried aluminiurs salt formed at anodic Moreover, cases have been re- Contamination of water by

out at a temperature below that areas, and obviously the pit of ported where water-line attack solis

of heavy metals, espe-

at which the brittle compound Is the solution and the hydrolytic has occurred even in the absence | cially

from

copper farmed. tendency of the salt are alike; of oxygen.

Other important and must be taken

uk explications

11 thecelerute the rate of corrosion. to consideration. Of the various water - line ttack suggest has been observed that contami- Impurities in akaninium,

ed include enhanced reactivity nation of water by copper deriv

iron

may also corsiderably

"ac-

even

and copper have the greatest ac- at the liquid surice, while aned from adjoining equipment

corrosion, other view is at It is connect may lead to celerating effect on corrosion.

Water-line attack of aluminiund with surface tcaston. In though the surface of aluminium has been known to occur with other

quarters It is considerett has received prefective treat- stationary

Water, sea water, salt that many instances of water-

ment. solutions, and weak citric acid- the attuck may be due to the the protective skin ad-

sodium chloride solutions. It Ana that

has been shown. in the case of heres to the water-air instead of the latter types of solutions, that to the metal-water interface, carrosion at the liquid-nir inter- thus exposing the metal. face is influenced by temperature concentration of suit und the pH of the solution.

Oxygen Important

has also been shown that oxygen plays an Im- portant part in water-line atluck by sea water, since there is no

The author's conclusion is thut the mechanism of the attack of aiceninium at the water-line is compliented and not yel fully understood.

varies

The form of attack which la meat damaging to alumlalur equipment and pipe systems le

to

ونا

Grab Makers

Claim Lead

pitting, and this is considered With 60 different govern-

brotight about by

ments on its order book, a chlorides and sulphates, par North of England firm of grab ticularly the former, in the water.

Investigatoru

makers clainis to have estab. the causes lished a leading world position of localised corrosion by in this vital field of production. bard Industrial waters have How vital can be seen from Effect Of Tap-water concluded, however, that the record of some, of the usos is due to tha simultaneous to which is equipment is today There is much evidence that presence of chlories and bicar- being put, "Priestman" grabs are marked action if the air is ex- the corrosion of aluminium by honates, and it is been shown removing boulders on the St. pelled by boiling It has been i

hidden rocks considerably that local attack could be pre-Lawrence River, tap-water noted that the deposit which;

Teneriffe forms at the liquid-air interface with the nature of the water and ven.ed by the addition of small from trade routes in

its dissolved mineral constituents, quantities of nitrates or chrom Harbour, handling cargues of palm has a strongly acid resetion.

the total even though

kernels and

Africa, amount utes.

peanuts In The presence of this seld deposit S

coment In India, coal on the scems to rule out the possibilty Present is very small (rarely ex-

Waters Aluminium Cans ceeding 0.1 per cent.).

· Cockside cranes in Spain, pitprops of the water-line attack being

531 Scandinavia, carrying out due to "differential-neration" cur- containing free seld, and parti-

cularly those containing frco Regarding alundulum for pack- archaeological research and gyp rents and solution of the film of alkali or chlorides, are likely to ing materials, cluminium-coated sum in South Africa, cryolite in oxide through the accumulation prove corrosive.

steel, it is said, is likely to find Spitzbergen, driftwood from the The objectionable dark stain, many applications as a substitute upstream face of a Blue Nile dam. sometimes observed on the both for tinplate end galvanised clay in Brazil, and cosi, iron ore. surface of

tlimber aluminium cook-sheeting, but dificulties, yet to sugar beet, grain,

and utensils, is due, BC- be overcome, stand in the way chemicals in ports, factories, coul

mines, and power stations.

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236-A, Hong Kong & Shanghai

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Tel. 28904.

H. W. SUTTON,

Manager.

The firm (Pricatman Bros. Ltd., of Halderness Foundry. Hull) claim to produce grabe for every purpose to which the grab can be put, whether it be handling household refuse for tocal authorities or taking sam- plan from the ocean bed two and half mitem below the surg face for scientific research. Today, nearly half * much tonnage again is being produced by this firm as compared with 1038. Yet its production staff has risen by only 10 per cent.

WORK STARTS ON · ALUMINIUM BRIDGE

Work has just begun in Britain on the world's first aluminium alloy, bascule bridge. It will apun -n-dock-entrance 00: feet wide at. Bunderland and will cost £83,- 000

it will Its

be less than Each that of a railway engine. span can be raised in a little over a minute by a motor of only 20 horsepower. For a steel Bridge of simllar, dimensions at least. 50 horsepower would be required.

METAL WINDOWS.....

by

GIBBONS

GILMAN & COMPANY LTD.

ENGINEERING DEPARTMENT Telephono 31146

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