| abstract |
Substituted diphenols, phenyl ethers containing two oxygen atoms attached to a benzene nucleus, and naphthols are more practically effective than previously known additives in stabilizing tin (II) salts, in electrolyte solutions useful for coloring anodized aluminum by electrolysis therein, against oxidation to tin(IV) by reaction with ambient oxygen. Preferred additives include 2-tert-butyl-1,4-dihydroxybenzene, methylhydroquinone, trimethylhydroquinone, 4-hydroxynaphthalene-2,7-disulfonic acid, and p-hydroxyanisole. If p-toluenesulfonic acid or napthalene sulfonic acid are also used in the electrolyte, the throwing power can be greatly improved. |