How to quickly test electroplating quality?

January 24, 2021

Some manufacturers produce wheel nuts and wheel bolts are easy to rust? The cause of the problem is that the plating quality is not up to standard. 

The common methods to test plating quality are: neutral salt fog test (NSS test) , acetate fog test (ASS test) and copper salt accelerated acetate fog test (CASS test) , but all three methods take several hours, tens, hundreds of hours. 

So how do you get accurate results quickly? 

We can pass an "electrolyte thickness gauge" . Through 5 minutes of testing, fast reading to get coating thickness and potential difference data, so as to immediately determine whether the quality of electroplating qualified or not.

The process of electroplating is to add layer upon layer.

No.1  Nickel (semi-bright nickel)

No.2  Nickel (bright nickel)

No.3  Nickel (high sulfur nickel)

No.4  Chromium (mainly for decoration)

No.5  Sealed (further anti-rust)

electroplating process

Testing the thickness of the coating is the process of stripping, layer by layer peeling down.

1. Stripping the surface layer of chromium by the chemical reaction between the measuring electrolyte KJ-2 and the chromium layer. When the potion touches the nickel, the chemical reaction stops. 

2. Change the other measuring electrolyte KJ-10 to react with the nickel layer and peel off all the nickel layers. When the potion hits the steel, it stops the chemical reaction. The thickness of the nickel layer is thus measured.

detection of coating thickness

The role of potential difference

1. potential difference can make coating adhesion stronger, more solid.

There is a potential difference between the coating, it will form a concave-convex bite state, so that the contact surface is larger, layer bite, coating more solid, not easy to fall off. 

If there is no potential difference, each layer and each layer is only flat lamination, coating easy peeling.

2. The potential difference can weaken the corrosion intensity and delay the corrosion time. 

When the corrosion force seeps down from the surface, the corrosion force will be refracted on the concave-convex surface because of the potential difference, and the corrosion force will be weakened after each refraction, thus delaying the time of the product being corroded. 


If there is no potential difference, corrosion force vertical downward penetration, will soon corrode all the coating, contact with the steel inside, resulting in rapid rusting.

the role of rotential difference

Therefore, to enhance the ability of anti-rust products

1. To increase the thickness of the nickel layer, 

2. To control the potential difference. 

3. The thicker the nickel layer, the more layers, the better.


The following is the test report of the tire nut in our factory.

potentail curve of multi nickel coating

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