Hard Chrome Adhesion

Q. What are the tests other than heat treatment/grinding to check the adhesion of hard chrome deposit? we are doing extra plating and then grinding as per the requirement and in that way adhesion is also checked. But is it possible to plate the required thickness and adhesion also to be checked. please advise. Thanks and Regards.

A. An age old problem..... to verify chrome plated parts have acceptable adhesion. Of course one can't see the adhesion without disturbing the chrome and the base metal by bending, cutting, flexing or chiseling away at it. An ideal situation is a customer who allows permission to sacrifice a part for testing. This is the most convincing way to show conformance, but spare parts are seldom available.

Most aircraft and Industry hard chromium plating specifications require the additional chrome plating of "test panels" to represent the actual parts being plated. Test panels are often made of the same material and harness (heat treatment) as the parts themselves or close to it. The more common test panels for hard chrome adhesion are usually one of two types

1.) 1" x 4" x .040 4130 annealed STL panel - for the "bend test"

2.) 1" diameter hardened / notched rod for a "chisel test".

This type of testing is usually done on a weekly or periodic basis or by "lot" and the idea is, during that period between tests, all the customer parts you chrome plate are represented by those test panels. If the panels pass the parts plated are acceptable. If a test panels fail then the parts are "suspect" and further evaluation is necessary to qualify the lot.

Many factors can affect the adhesion of the hard chrome on a substrate so test panels are not the 'catch all" answer, but at least they provide a measure of confidence in a particular chrome plating bath. The rest is up to the platers themselves to ensure they have set the job up according to the best standards and practices.

Thank you for the question.

Randy Taylor