Makeup of a Woods Nickel Strike
Q. I am new to the plating industry and am having problems with some of the formulations used in our plating shop. In particular I am confused about the makeup of a Woods nickel strike bath. Some of the terminology that is used is different than the terminology I learned in my chemistry classes. Can you give me some help with this problem? F.P.
A. I can understand your confusion. I am originally trained as a chemist and still wonder about some of the terms used in the world of electroplating. But here are a few pointers for you and hopefully they will help you in preparing your Woods nickel strike.
Typically, the commercially available acid is considered to be 100% acid. If a formulation calls for 10% hydrochloric acid, it means 10 mL/100 mL (10 mL/100 mL × 100 = 10%) or 12.5 oz/gal (12.5 oz/128 oz × 100 = ~10%) of standard 22°-Baumé hydrochloric acid in water. If we are talking about concentrations in grams per liter, for example 142 g/L, you would divide by the density of the hydrochloric acid (1.19 g/mL). This would be 142 g/L divided by 1.19 g/mL or 119.3 mL/L.
In the case of the Woods nickel strike one standard formulation calls for 6 oz/gal of nickel in 10 –12% hydrochloric acid. The 119.3 mL/L is close to the 12% 119.3 mL/L/1000mL/L × 100 = 11.93% or ~12%.
If more than one concentration of a commercially available acid is available, i.e., nitric or sulfuric acid, the concentration of the acid in degrees Baumé to be used is usually specified. If the concentration is not given, which by today’s standards is considered inadequate, it is assuming that the more commonly available commercial acid is to be used.