How do you test coating thickness? What are the common methods?
Destructive testing: Metallography (section observation), Dissolution method (chemical dissolution followed by weighing).
Non-destructive testing: Magnetic thickness gauge (for ferrous substrates), Eddy current thickness gauge (for non-ferrous substrates).
How is the corrosion resistance of a coating tested?
Neutral salt spray test (NSS): The most commonly used test, which measures the corrosion time of the coating in a salt spray environment.
Acetic acid spray test (ASS): A more stringent test, simulating an acidic environment.
Immersion test: Immersing the part in a specific solution (such as salt water) and observing the corrosion.
What are the methods for testing adhesion?
Bend test: Bend the part 180° and observe if the coating peels off.
Scratch test: Use a blade to make a cross-shaped cut, apply tape, and then tear it off. If no peeling occurs, the coating passes.
Impact test: Use a heavy hammer to strike the coating to check for cracks or peeling.
How can the impurity content in the plating solution be controlled?
Filter the plating solution regularly to remove solid impurities. The "electrolytic purification method" uses low-current electrolysis to remove metallic impurities (such as copper and iron).
High-purity raw materials are used when replenishing the reagents to reduce impurity introduction.
What are the criteria for determining the appearance quality of the coating?
No defects such as pinholes, cracks, flaking, or blackening.
Bright coatings must be uniformly bright with no noticeable color differences; matte coatings must have a consistent color.
Appearance requirements must meet customer or industry standards (such as GB/T 9799 and ISO 2081).