Abstract
From the curves of cathodic and anodic polarization of composite metals except chromium in two kinds of multi-layer coating (copper-nickel-chromium and duplex nickel-chromium) in various corrosive solutions, local corrosion cell effect between copper and bright nickel as well as that between semibright nickel and bright nickel were presumed. The same types of corrosive solution as in the previous report were used.
Furthermore, open-circuit and closed-circuit corrosion rates of each couple were compared by means of corrosion loss weighing.
As a result, the following conclusions were obtained.
1. In copper-bright nickel cell, copper is cathodically protected effectively by bright nickel in sulfur oxide solutions. The same couple is less active in acid salt solution and almost ineffective in CASS Test solutions.
2. In duplex nickel cell, semibright nickel is effectively protected by bright nickel in any other solutions than sulfurous acid solution.
