Abstract: A process and compositions for detecting improperly processed areas in heat treated aluminum are disclosed. A solution containing an acid or a base and an oxidizing agent and, if desired, a color enhancing ingredient is applied to an aluminum object to produce a color difference between those areas of the surface of the object which have been properly hardened and the areas resulting from improper heat treatment. The solution can be applied to the aluminum by brushing, swabbing, immersion or spraying. The acid or base in the solution attack the aluminum surface so that the oxidizing agent in the solution can react with the aluminum to produce the aforementioned color differential.

Abstract: An improved composition and process for chemically milling titanium, refractory metals, and their alloys, resulting in decreased absorption of hydrogen, thus allowing chemical milling of beta titanium and alpha beta titanium, which normally cannot be chemically milled in conventional chemical milling solutions because of hydrogen embrittlement.The chemical milling solution itself consists of a mixture of nitric acid; hydrofluoric acid or fluoride salts; derivatives of carbonic acid, such as carbamide; derivatives of monocarboxylic acids containing alkali metal ions, such as sodium benzoate; and a source of sodium ions compatible with the remainder of the composition, preferably sodium nitrate.The addition of sodium benzoate results in a more uniform metal removal rate, thus permitting the producing of high precision parts.