Abstract
Following a historical review of the use of alternating current for anodising purposes, the paper describes the application of a c to oxalic acid and sulphuric acid electrolytes, including the development of integral colours in oxalic acid, and very stable and light fast colours in sulphuric acid by formation of metallic sulphides in the anodic coating. The paper describes a novel modification of the basic sulphuric acid process designed to offset the natural electrochemical reaction of a c so as to produce a coating having properties more akin to a d c film, and summarises the advantages of such a process, covered by a recent British Patent13.

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