Some articles such as automobile components that have been constructed from steel and/or aluminum alloy parts are now being fitted with magnesium parts whose surfaces may need to be protected against corrosion. To do this an e-coating pre-film may be formed on the part's magnesium surfaces by exposing it to a conventional e-coating emulsion. And there is no need to supply a current or potential to the part or component. Magnesium's high reactivity with acidic or neutral aqueous mediums is itself a sufficient driving force to facilitate the deposition of an e-coating pre-film. At the same time any steel or aluminum alloy parts will remain unaffected. The article with a protective e-coating pre-film formed solely on its magnesium surfaces may now be advanced through a paint-line that includes conventional processes aimed at treating the component's steel and aluminum alloy parts. The process may be practiced where the magnesium surface comprises a magnesium-containing conversion or anodized coating.
