Zinc plating of compression springs(2000)
We are currently encountering a problem with plated compression springs. The springs are used in an automotive switch. Previous tests on unplated springs (spring steel) resulted in the exposure of the springs to water, with the resulting corrosion. These springs were completely rusted and corroded. As an alternative to this, we decided to resort to corrosion protection using zinc plating (barrel plating). Corrosion protection has improved tremendously. However, we are now faced with another more serious problem. After a series of cycles, the springs are breaking. Test repeats have confirmed this result. Tests on the unplated springs did not result in any breakages of the springs. Is this due to the zinc plating process? I think that the acid pickling performed in the pretreatment process is partly to blame in reducing the mechanical properties of the spring.
Is there anyone else who has had experience with this type of problem?
A. The springs have to be baked for stress relief within 24 hours and preferably within 2 hours. Both the acid and the plating process are contributing factors, but proper baking should eliminate virtually all failures.
Ted Mooney, P.E. RET
Pine Beach, New Jersey