The coating/plating analysis

Background  information
In order to prevent the problem of corrosion, wear, or fatigue fracture appeared in the process of storage and using of the steel material. all kinds of surface coating treatment has been widely used.Including the surface has been infiltrate with zinc, Al, Cr, V, Nb, B, etc. Coating technology include hot dip, electroplating, electroless plating and heat treatment, etc. Paint/coating not only can decorate the appearance of the parts and repair the defects of parts surface , but also  can give special performance to the parts surface, including making the surface hardness , wear resistance, corrosion resistance, electrical conductivity and high temperature oxidation resistance to be higher. Involved products include home appliances, automobile, doors and Windows, metal fasteners and electronic products, etc.

The tested  items
 detecting the thickness of the coating,

Coating thickness is the vertical distance from the surface to the interface boundary layer the situation of  only having compound layer and the straight interface  ,the determination of deep layer is simple. And  in the permeation of diffusion layer, layer thickness should include compound layer and diffusion layer. the determinated methods of coating thickness include  Coulomb's law method, metallographic method, eddy current method and X-ray fluorescence method.

Coating porosity test

In the process of permeation and  Immersion , the  elements of permeation spread in-diffusion, and iron elements spread out-diffusion, and  the diffuse velocity of them is different, so in the compound layer, especially where it is near the surface will inevitably
produce pore (or loose) .and .the quantity, size and distribution will directly affect the weldability of steel and service performance.

Coating crack test
In the process of management ,  it could let a brittle compound layer crack as the phase transformation stress,the  crack also directly affect the service performance, therefore we should test the characteristics of the crack,  that’s to say,we should test the crack length, number and distribution state.
In addition, the metal laboratory also can provide the coating composition analysis, surface stain analysis, surface hardness and adhesion strength analysis.


Testing standard 

Tested item

Testing standard

Plating thickness - coulomb's law method

 GB/T 4955-2005

Plating thickness - metallographic method

 QB/T 3817-1999

 Plating thickness - electron microscope method

 JB/T 7503-1994,ASTM B748-1990(2006)

 Plating thickness - X ray method

 GB/T 12961

The quality of the galvanized layer

 ( weight)

 GB/T 1839-2008,ISO 1460:1992(E)

 Coating composition analysis 

( spectroscopy )

 GB/T 17359-1998

 Adhesion strength - methods of thermal  shock / bending / thermal shock 

(quenching )

 SJ 20130-1992,ASTM B571,ISO 2819

Adhesion strength - hot and cold cycle ,  chromium coating crack , chromiumplating porosity

 GB/T 12600