UK Aluminium Industry Fact Sheet 2 Aluminium （英国铝行业简报2铝）.pdf

UK Aluminium Industry Fact Sheet 2 Aluminium and Corrosion UK Aluminium Industry Fact Sheet 2 : Aluminium and Corrosion +44(0)121 601 6363 .uk 1 Introduction Electrochemical Aspects Although aluminium is a very reactive metal with a of Corrosion high affinity for oxygen, the metal is highly resistant Reactions to most environments and to a great variety of chemical agents. This resistance is due to the inert Any corrosion reaction in aqueous solution must and protective character of the aluminium oxide involve oxidation (anodic reaction) of the metal film which forms on the metal surface. In most and reduction (cathodic reaction) of a species environments, the rate of corrosion of aluminium in solution, with consequent electron transfer decreases rapidly with time. In only a few cases, between the two reactants. The anodic and e.g. caustic soda, does the corrosion rate cathodic reactions occur at the same rate and approximate to the linear. simultaneously upon a metal’s surface, therefore the metal is electrically charged, and thus the Although the oxide film is extremely thin, between rate of oxidation is equal to the rate of reduction. 50 and 100 Angstroms, it forms a protective For example in this situation, the corrosion of barrier between the metal and the surrounding aluminium in water may be represented by the two medium as soon as the metal comes into contact half reactions:- with an oxidising environment, such as water. The physical-chemical stability of the oxide