Aluminium electrochemical corrosion

Coatings consisting of a mixture of equal parts of cadmium and tin are particularly suitable for the protection of steel fasteners in contact with aluminium in aircraft structures where electrochemical corrosive attack is prone to occur under adverse conditions. The protection afforded is... 

Chemical and Electrochemical Corrosion of Pile Materials Under Radiation, Since uranium is readily oxidized, it must be protected from the water by a sheath or coating. Also, for the external cooling, a lining tube must be placed in the graphite. With water as the coolant, these two (the sheath and tube) must be of the same material or of two materials close together in the electrochemical series to suppress electrochemical corrosion. Of the few suitable materials, which have low danger coefficients and are not attacked appreciably by hot water, etc., the most promising are, in order, beryllium and aluminimn. While the former is more desirable also for its hardness and resistance to wear, the limited supply of beryllium available plus the lack of commercial development make aluminium with its more extensive commercial production and development practically the only alternative, imtil such time as beryllium or beryllium-aluminimn alloys can compete or surpass aluminium or unless further corrosion tests prohibit the use of aluminium and force the development of Be or Be-Al. 

A second danger point for electrochemical corrosion is at the junction of the aluminium and the steel which must comprise the water cooling system outside of the pile. Tests on inhibitors and corrosion from H2O2, O2, H2, etc. in hot water while under radiation seem to indicate no great danger from corrosion at these junctions, if proper precautions are taken. 

All plastics are permeable to moisture, and this can lead to failures caused by (i) electrochemical corrosion of aluminium metallisation (ii) dendritic growths between gold metallisation tracks and (iii) the corrosion of gold if suitable complexing agents are present. The rate of degradation is affected by many factors but two of the most important are the amount of ionic contamination which can be leached from the plastic and the quality of the passivation layer which is now present on the surface of all ICs. 

R.L. Chance, Electrochemical corrosion of an aluminium alloy in cavitating ethylene glycol solutions , in W.H. Ailor (ed). Engine Coolant Testing State of the Art, ASTM STP 705, American Society for Testing and Materials, Philadelphia (1980) pp. 270-283. 

As a matter of principle, in the absence of humidity, a dry powder has no action on aluminium, because corrosion as an electrochemical reaction can develop only in an aqueous medium. Salts that are very insoluble in water, therefore, generally have no action on aluminium. 

Froment, M. and Vignaud, C., Study of Intergranular Corrosion of Aluminium Using Bicrystals , J. Electrochem. Soc., 119, 216C (1972)... 

Videm, K., Pitting Corrosion of Aluminium in Contact with Stainless Steel , Proc. Conf. on Corrosion Reactor Mater., Salzburg, Austria, 1, 391 (1962) C.A., 60, 1412g Lyon, D. H., Salva, S. J. and Shaw, B. C., Etch Pits in Germanium Detection and Effects , J. Electrochem. Soc., 110, 184c (1963)... 

The electrochemical properties of zinc also have a large bearing on its corrosion behaviour. Zinc is negative to Eh /h2 and magnesium and aluminium excepted, to most other metals commonly encountered, including those found in the less pure forms of zinc. This means that when zinc is in contact with these metals sacrificial electrochemical action can take place, with zinc forming the anode. Contact with other metals and impurities can... 

Fischer, K. P., Thomason, W. H. and Finnegan, J. E., Electrochemical Performance of Flame Sprayed Aluminium Coatings of Steel in Water , Paper No. 360, Corrosion/87, San Fransisco, USA, March (1987)... 

Electrochemistry is widely used in industry, for example in effluent treatment, corrosion prevention and electroplating as well as in electrochemical synthesis. Electrochemical synthesis is a well-established technology for major processes such as aluminium and chlorine production there is, however, increased interest in the use of electrochemistry for clean synthesis of fine chemicals. The possible green benefits of using electrochemical synthesis include ... 

De Morais NLPA, Brett CMA (2002) Influence of power ultrasound on the corrosion of aluminium and high speed steel. J Appl Electrochem 32 653-660... 

The selective hydrogenation of enones is also achieved in a process employing an aluminium-mckel system. This process is electrochemical in nature but does not use an external electron source. Dissolving aluminium is used as the reducing agent with a catalytic amount of nickel chloride present in the tetrahydrofuran solvent. Finely divided nickel is deposited on tlie aluminium and this sets up local corrosion cells. Aluminium dissolves and tlie released electrons are transferred to nickel where protons are reduced to hydrogen. The hydrogen-nickel system then reduces the alkene bond in the enone [153]. 

The galvanic or contact method was the precursor to electrochemical treatment [283]. In an electrolytically conducting solution, the artifact is brought into contact with a piece of a less noble metal— usually zinc or aluminium. While the metal corrodes, the electrons supplied to the object allow the reduction of the tarnish layer. Although simple, this method presents some drawbacks, like the progressive contamination of the solution by the corrosion products of the active metal and also limitations with respect to the choice of applicable solution. 

Electrochemical protection can be achieved by forming an electrolytic cell in which the anode material is more easily corroded than the metal it is desired to protect. This is the case of zinc in contact with iron (Fig. 16.11) in this example there is a sort of cathodic protection. Protection of ship hulls, of subterranean pipeline tubings, of oil rigs, etc. is often done using sacrificial anodes that are substituted as necessary. The requisites for a good sacrificial anode are, besides its preferential corrosion, slow corrosion kinetics and non-passivation. Sacrificial anodes in use are, for this reason, normally of zinc, magnesium, or aluminium... 

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