If you’ve ever had the unfortunate experience of a metal coating become unattached from the surface of a part, then you recognize the value of reliable adhesion testing. One way to accomplish this is to perform a cutting test for quality. There are several methods for cutting metal that can provide the desired result, without damaging the underlying substrate.
Grind-Saw Test
This cutting test process involves using a rough emery wheel or hacksaw. When using an emery wheel, the part is placed against the wheel in a manner that uses a series of jerky strokes to cut from the substrate toward the metal deposit. If a hacksaw is the cutting tool of choice, the method should entail sawing in the direction that separates the coating from the substrate. In either case, poor adhesion is present if peeling or lifting occurs. The grind-saw cutting test process is a suitable choice for hard and brittle coatings, but it will not work as well on softer, thinner finishes.
Why is cutting tested for electroplating purposes? Coating materials that work best with this test include:
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Scribe-Grid Test
The scribe-grid test is another method that involves cutting the metal. A sharp, hardened steel tool is used to scribe either two parallel lines or create a grid pattern on the coating surface. The distance between the scribed lines should be about 10 times the nominal coating thickness, with a minimum of 0.4 mm. The level of pressure applied during scribing should be enough to reach the substrate surface with one stroke. Insufficient adhesion exists if any of the metal coating between the scribed lines breaks away from the substrate.
Thinner coatings tend to work best with this cutting test process, as thicker coatings may require using a chisel or similar tool to pry the deposit from the substrate. The most appropriate metals for the scribe-grid test are copper and nickel.
Experience Is Helpful When Interpreting Cutting Test Results
As with most standard testing processes for metal coating adhesion, the results of the cutting tests are interpreted by using qualitative as opposed to quantitative methods. This makes these processes more subjective and requires a high level of expertise to ensure an accurate interpretation.
Sharretts Plating Company Has Extensive Cutting Test Experience
SPC has more than 90 years of metal finishing experience. We know how to conduct an effective cutting test process that delivers consistent, reliable results. We also have the ability to accurately interpret test results to determine if sufficient adhesion of the metal coating has occurred. Contact us to learn more about cutting metal to test adhesion and how it can benefit your manufacturing processes.
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"I would like to thank you for the help you have provided us in developing an electroless nickel plating technique on an unusual substrate. The sample platings you provided show that we should be able to reach our goals. I especially appreciate your willingness to take on an unusual job, with the uncertainties that that entails...We are looking forward to working with you in the future on our plating needs."
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