Engineers explain: Performance testing of automotive plastic electroplated trim parts

1 Detection of coating thickness, potential difference, number of micro-holes and micro-cracks

①For the detection of coating thickness, the main methods currently used are microscopy, coulomb method and X-Ray method.

See Table 1 for the methods adopted by internationally renowned automobile companies for the coating thickness of plastic electroplated parts. According to the plating thickness requirements of the standard, judge whether the plating is qualified.

②Detection of multilayer nickel potential difference

The multi-layer nickel potential difference test of major automobile companies uses Steptest to measure the potential difference between microporous nickel and bright nickel, the potential difference between bright nickel and semi-bright nickel, and the difference between high-sulfur nickel and bright nickel. Potential difference.

Figure 1 shows the potential difference between the nickel layers and the thickness of each layer of nickel. At present, the requirements of automobile companies are almost the same. Take General Motors’ potential difference requirements as an example: microporous nickel-bright nickel: 10-40mv, bright nickel～semi-bright nickel: 100~200mv, high-sulfur nickel～bright nickel: 15～ 40mv.

Figure 1

③Detection of the number of micro-holes and micro-cracks

There are usually two test methods for the number of micropores, the copper deposition measurement method and the active corrosion point measurement evaluation method.

The number of micro-holes in the copper deposition measurement method of major automobile companies is greater than 10,000 holes/cm², and the active corrosion point measurement and evaluation method requires more than 2000 holes/cm². The number of micro-cracks is at least 250-800/cm², and they are uniformly distributed in a grid in all directions. Too few micro-holes and micro-cracks will reduce the anti-corrosion effect of the coating.

2 Detection of adhesion of automobile plastic electroplated parts

There are commonly j methods for testing the adhesion of plastic coatings, such as the cross-cut method, the sawing method and the peeling method.

The cross-cut method and sawing method are based on the test results to visually judge, while the peeling method is to judge whether the coating adhesion is qualified or not based on the peel strength measured by the test.

General Motors currently uses the 90° peel method to test the peel strength of the coating, while Volkswagen uses the float method to test the peel strength of the coating and the substrate.

3 Temperature test related to automobile plastic electroplating parts

The testing standards for plastic plating parts of major automobile companies in the world usually include three types of temperature testing, temperature storage, rapid temperature change, and temperature cycle testing. Three different temperature types are used to check the appearance, dimensional stability and dimensional stability of the plastic plating parts after the test. Coating adhesion.

4 Corrosion resistance test of coating

Currently, major automobile companies generally use CASS testing for the corrosion testing of plastic coatings. The specific testing time may vary slightly between major companies, and the testing time for interior and exterior parts is also different.

In short, the testing methods for automotive plastic electroplated trim parts are becoming more and more perfect. In addition to the above-mentioned testing requirements, for example, General Motors requires that plastic electroplated exterior parts be subjected to gravel impact tests, and Honda requires ductility testing in accordance with ASTM B490.