PURPOSE: To prevent the generation of contact corrosion of different metals caused by the deterioration of a film, in immersing different metals, after coating in a contacted state, in a corrosive aqueous solution, by separately providing selective cation permeating action and selective anion permeating action to the films on the surfaces of both metals in a layered form.
CONSTITUTION: A paint having selective anion permeating action is applied to the surface of a metal forming an anode among two kinds of metals contacted in an aqueous solution as an under coat layer. In addition, a paint having selective cation permeating action is applied onto the the under coat layer or a cation exchange film is adhered and applied by an under coat or an ion exchange composite film is adhered and applied by the under coat so as to direct the anion exchange side to the metal side and the cation exchange side to the solution side. In another method, a paint having cation permeating action is applied to a metal surface forming a cathode as an under coat layer and a paint having anion permeating action is applied thereon. by these methods or other methods, the ion electrophoresis between both metals is blocked to prevent contact corrosion.