basic introduction

In order to prevent corrosion, abrasion or fatigue fracture of steel materials during storage, transportation and use, various surface coating treatments have been widely used. Including surface infiltration of Zn, Al, Cr, V, Nb, B, etc. The coating process includes hot dipping, electroplating, chemical plating and heat treatment infiltration. Coating/plating can not only decorate the appearance of parts and repair surface defects of parts, but also give parts surface special properties, including improving surface hardness, wear resistance, corrosion resistance, electrical conductivity and high temperature oxidation resistance. The products involved include household appliances, automobiles, doors and windows, metal fasteners and electronic products.

Test items

Coating thickness detection

The thickness of the coating refers to the vertical distance from the surface to the boundary of the permeation interface. For the case where only the compound layer is formed and the interface is flat, the measurement of the layer depth is very simple. For the infiltrated layer with a diffusion layer, the layer thickness should include the compound layer and the diffusion layer. The coating thickness measurement methods include Coulomb method, metallographic method, eddy current method and X-ray fluorescence method.

Coating porosity detection

In the process of infiltration and immersion, the infiltration element diffuses inwards, while the iron element diffuses outwards, but the diffusion speed of the two is different, so pores (or looseness) are inevitably generated in the compound layer, especially near the surface. The quantity, size and distribution directly affect the weldability and service performance of the steel.

Coating crack detection

During the treatment process, due to the phase change stress, the brittle compound layer may be cracked, and the crack directly affects the service performance. Therefore, the characteristics of the crack, that is, the length, number and distribution of cracks should be checked.

In addition, the metal laboratory can also provide coating composition analysis, surface stain analysis, surface hardness analysis and adhesion strength analysis.

Testing standards

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