The first is to improve the rust resistance of
stainless steel plates. Among the stainless steel materials, the chromium content of martensitic stainless steel such as 2Gr13, 3Gr13, 9Gr18, etc. is greater than 12%. Other stainless steels that do not contain nickel or only contain a small amount of nickel are prone to discoloration and corrosion in the atmospheric environment. In order to enhance the corrosion resistance of stainless steel plates It can be plated with decorative chrome or hard chrome.
The second is to improve the appearance. Stainless steel plate products and electroplated decorative chrome are assembled together, and the surface will have significant differences. In order to keep the appearance and color the same, the surface of stainless steel plate is often chrome-plated.
In addition, the hardness of the stainless steel plate can be enhanced. In particular, the hardness of austenitic stainless steel will be relatively low. Although the corrosion resistance is relatively good, the wear resistance of the material is poor, so hard chrome plating is required to increase the hardness, improve the wear resistance, and prolong the service life of the stainless steel plate.
It can also be coated with a milky white chrome layer, which is to obtain a soft coating. For example, milky white hard chrome can be plated on the scale or plate of a stainless steel measuring tool, which is not only highly decorative, but also has good optical performance.
The general method for chrome-plating stainless steel plate is to use the method of activation and pre-nickel plating to obtain the bottom layer before chrome-plating stainless steel plate, and then chrome-plate the nickel-plated layer to obtain a chrome layer with excellent bonding force.
Because stainless steel plates have a wide variety of chemical compositions, shapes, and pre-plating states, it is necessary to use appropriate process flow and process specifications, as well as special tools and fixtures, according to the actual situation.
For the quality inspection of the chrome-plated layer on the surface of the stainless steel plate, first of all, it is necessary to look at the appearance of the lower surface. The surface of the plate is required to have uniform gloss, fine crystallization, no roughness, no peeling, no bubbling, no bottom leakage, no darkening, and no burning coke.
Regarding the binding force, the cross-scratch method means no peeling, and the bending test means that the fracture will not peel after the sheet is broken.
Microhardness is measured using a microhardness tester, but it can only be measured accurately when the thickness of the chromium layer is not less than 20um.
The last is to observe the porosity. You can use the filter paper method to measure the pores. Put the filter paper soaked in the test solution on the test surface. No air bubbles should be left under the filter paper. After 10 minutes of sticking time, remove the filter paper and dry it. Then look at the number of blue dots, which is the number of pores on the chromium. Generally, the porosity is required to be within 1-3/cm2 to be qualified. The lower the porosity, the higher the corrosion resistance. The thicker the chrome layer, the lower the porosity.
