Worm Tracks and Pits
Q. What causes pitting and worm tracks in satin nickel? R.R.
A. Modern satin nickel plating baths usually contain additives of various types to give you the satin-like finish. The first thing I would do is talk to your chemical vendor and determine if he has any possible explanations and solutions for your problem. Your supplier knows the chemistry of the plating bath and may have had this problem before. What else can you consider in this particular problem?
Pitting in a nickel plating bath can be caused by bubbles sticking to the surface of the part as well as particulate matter suspended in the plating solution. In a classic nickel plating bath, small amounts of wetting agents are used to keep the surface tension of the bath under control. This serves to allow small bubbles to slide off the surface of the part as they are formed. Other causes of pitting are low boric acid concentration and iron in the plating bath.
Worm tracks can be caused by the base material contract when cooled. For example, plastic components plated with a metal such as nickel may appear okay initially, but when the parts are put into use in a cool or cold environment, worm tracks may form. What is going on here in simple terms is that the base material is shrinking away from the plated layer.
Your email did not give any information about the process you are using nor the materials that you are plating. If you email me additional details I may be able to give you a more detailed answer.