Abstract: Methods for treating metallic surfaces, such as aluminum and chromium alloys, are disclosed, including contacting the metallic surfaces with an aqueous solution containing a sulfate providing agent, such as sulfuric acid or alkali metal persulfate, an oxidizing agent for the sulfate providing agent, an alkali metal permanganate and an alkali metal carbonate, so as to provide a passivity surface layer on the metallic surface substantially comprising manganese, oxygen, sulfur and carbon. Aqueous solutions for providing these passivity layers are also disclosed.