Patent ID: 7695771

Claim:
A process for forming a non-chromate conversion coating on surfaces of magnesium or magnesium alloys comprising the steps of: providing clean surface of magnesium or a magnesium alloy; contacting said surface with a process solution; whereby said process solution is an aqueous solution or an aqueous dispersion having a pH in the range from 0.5 to 3 and comprising: at least one fluorosilicon acid in the range of from 4 to 100 g/L, at least one water-soluble pH adjustment agent, wherein the at least one water-soluble pH adjustment agent is at least one alkaline silicon compound selected from the group consisting of a silane, a silanol, a siloxane and a polysiloxane, which has at least one of an amino group, an ureido group or an imino group, wherein the non-chromate conversion coating is formed with the aid of the process solution and wherein the non-chromate conversion coating is light gray to black.