Process for the treatment of iron - white mat in order to avoid the black and white iron - resulting

摘要

Matte tin plate, which is resistant to discolouration in storage and which will not darken in baking incident to lacquering and lithographing, is produced on a low-carbon steel base by electrolytically depositing a layer of tin, heating the layer to a temperature above 266 DEG F. but below 420 DEG F. to form a crystalline tin oxide film and subsequently treating the layer and film, e.g. electrolytically, in a chromate solution to superpose a film of chromium oxides on the tin oxide film. In an example tin is electroplated on a strip of low-carbon steel, the strip is dried, heated to above 400 DEG F. and below 420 DEG F., water quenched, and passed as cathode between anodes in an aqueous solution containing 24 g. sodium dichromate per 1. adjusted to a pH of 4.7 at 125 DEG F. and using 52 coulombs of current per sq. ft. of the strip. The treated strip is rinsed with cold water, dried with steam, and electrostatically oiled.