The Tunnel Etching of Aluminium

[摘要] The electrochemical potential for the active dissolution of aluminium in sodium chloride solution is found to belinearly related to the logarithm of the chloride ion concentration. The value ofE0calculated on the basis of thepostulated electrode reaction is approximately 0.3 V more negative than the experimental value and a similarinequality is observed for bromide and iodide electrolytes.The electrochemical etching of aluminium in chloride, bromide or iodide solutions is initiated at weak points inthe surface oxide film. Subsequent stages in the dissolution process involve a random attack leading to theformation of cavities and a selective attack leading to tunnelling. The dominance of one or other of thesedissolution modes is largely dependent upon the electrochemical parameters. It is suggested that the reason for thisdependency is associated with an alteration in the electrode potential for dissolution resulting from changes in thehalide ion concentration within the tunnel structure.

[学科分类] 工程和技术（综合）