Patent ID: 8187440

Claim:
A method of coating a magnesium-based substrate, the method comprising the steps of: applying a first potential of electric current to the magnesium-based substrate to thereby negatively charge and protect the magnesium-based substrate against magnesium dissolution; after applying, immersing the negatively charged magnesium-based substrate in an electrocoat coating composition; after immersing, applying a second potential of electric current between the magnesium-based substrate and a counter electrode to deposit a film from the electrocoat coating composition onto the magnesium-based substrate; wherein the second potential of electric current is greater than the first potential of electric current; and curing the film to form a cured film disposed on the magnesium-based substrate to thereby coat the magnesium-based substrate with the cured film; wherein applying the first potential of electric current controls magnesium dissolution of the magnesium-based substrate in the electrocoat coating composition before the cured film is formed and disposed on the magnesium-based substrate.