6. Bostik-Endurion process

This process, which originated in the UK (Pyrene Chemical Services Limited), appeared in France around 1960, but to our knowledge has not seen any industrial development in our country, due to the complexity of the range and its high cost price. However, we mention it because of its originality. It consists of depositing tin by chemical displacement on a layer of zinc and iron phosphates of at least 10 µm, or manganese and iron phosphates. This can then be colored in a hot aqueous solution (possible colors: black, brown, red, blue, green); finally, a wax, generally dissolved in white spirit, or an oil, is applied.

Corrosion resistance is improved compared to conventional phosphating, the appearance of the parts is very attractive, and the process allows parts of similar shapes or sizes to be indexed thanks to its coloring possibilities.