To create a semi bright nickel chromium plating use coumarin in the Watt baths which become prominent in the plating of automobile bampers. Introduce the use of coumarin will obtain a high-leveling, ductile, semibright, sulphur free nickel plate. This plate is easily buffed bright and then chromium plated to make more bright and resist to corrosive effect.
From the static roof exposure tests in industrial atmosphere, the corrosion protection with this chromium-plated double layered nickel coating was superior to even the good performance of the same total thickness of chromium plated sulphur-free buffed semibright nickel. This double layer nickel coating was an important step in obtaining greatly improved corrosion pits starting in the bright nickel underneath the pores in the top thin chromium plate are diverted laterally on reaching the more noble sulphur free nickel layer, thus greatly delaying the corrosion pitting penetration to the underlying steel or zinc show this sacrificial protection because the acidity of the industrial atmosphere was due mainly to moist sulphur dioxide which attacks sulphur-free nickel about as readily as nickel containing 0.08% sulphur. On the other hand, in the presence of acidic saline solutions, the sulphur containing nickel is attacked anodically more rapidly than sulphur-free nickel.
The neutral salt spray test was practically useless for predicting outdoor exposure results with nickel chromium and copper-nickel chromium plate. The development and extensive use of accelerated tests, proved to be of immense benefit in indicating that the double layered nickel plating system could confer greatly improved outdoor corrosion protection to copper plated zinc die casting as well as to steel articles, especially under acidic saline exposure.
To improve in diverting the corrosion pitting laterally were obtained by using a thin layer of nickel (1.2 – 2.5 μm), containing 0.15% sulphur, between the sulphur-free of nickel and the top bright nickel, containing 0.04 to 0.08% sulphur. The triple nickel layered nickel plate uses a 50:50 ratio of semibright to bright nickel instead of the 70:30 prefered ratio for the double nickel.
From the static roof exposure tests in industrial atmosphere, the corrosion protection with this chromium-plated double layered nickel coating was superior to even the good performance of the same total thickness of chromium plated sulphur-free buffed semibright nickel. This double layer nickel coating was an important step in obtaining greatly improved corrosion pits starting in the bright nickel underneath the pores in the top thin chromium plate are diverted laterally on reaching the more noble sulphur free nickel layer, thus greatly delaying the corrosion pitting penetration to the underlying steel or zinc show this sacrificial protection because the acidity of the industrial atmosphere was due mainly to moist sulphur dioxide which attacks sulphur-free nickel about as readily as nickel containing 0.08% sulphur. On the other hand, in the presence of acidic saline solutions, the sulphur containing nickel is attacked anodically more rapidly than sulphur-free nickel.
The neutral salt spray test was practically useless for predicting outdoor exposure results with nickel chromium and copper-nickel chromium plate. The development and extensive use of accelerated tests, proved to be of immense benefit in indicating that the double layered nickel plating system could confer greatly improved outdoor corrosion protection to copper plated zinc die casting as well as to steel articles, especially under acidic saline exposure.
To improve in diverting the corrosion pitting laterally were obtained by using a thin layer of nickel (1.2 – 2.5 μm), containing 0.15% sulphur, between the sulphur-free of nickel and the top bright nickel, containing 0.04 to 0.08% sulphur. The triple nickel layered nickel plate uses a 50:50 ratio of semibright to bright nickel instead of the 70:30 prefered ratio for the double nickel.