Brief Introduction
Material Quality: ABS
MOQ(Minimum order quantity): 3000pcs each design
Plating Method: Water Electroplating
Plating Color: Bright Chrome plating
1. The purpose of chrome plating:
1. Because the chromium layer is relatively inert, extremely hard and corrosion-resistant. Therefore, it is usually used as the outermost layer of electroplating (functional coating/decorative coating).
2. Because of the physical properties of chromium, it is extremely hard and corrosion-resistant. Therefore it is also commonly used in mold chromium plating (hard chrome plating).
2. Principle of bright chromium plating:
The chromium-plating solution mainly uses chromic anhydride to provide chromium ions, and sulfuric acid acts as a catalyst to form electroplated chromium.
Anodic reaction:
2H2O - 4e = O2 + 4 H+
2Cr3+ + 6H2O – 6e = 2CrO3 + 12H+
Pb + 2H2O – 4e = PbO2 + 4H+
Cathodic reaction:
Cr6+ + 6e = Cr
2 H+ + 2e = H2
3. Things to note:
1. Chromium strips cannot be used as anodes. In addition to the fact that chromium cannot be processed due to its physical properties, the chromium anode will dissolve into trivalent chromium with approximately 100% cathode efficiency, increasing the trivalent chromium content in the solution to the point where it cannot be processed. limits of acceptance;
2. Although pure lead is used by many "reversed rack plating" electroplating companies, the better anode material for corrosion is lead-tin or lead-antimony alloy (tin or antimony 5-10%);
3. The key is to control the bright agent content of the bright nickel cylinder, which must be kept at the middle and lower limits to facilitate chromium coating;
4. Special attention: when the concentration of chromic acid and sulfate changes, the ratio of chromic acid/sulfuric acid remains in the range of 100:1 or 200:1;
5. Except for the self-adjusting solution, sulfate radicals are almost always brought in by sulfuric acid. Sulfuric acid does not consume, it just brings out losses;
6. In order to overcome the current density deviation problem, auxiliary anodes or auxiliary cathodes are often used;
7. The chromium plating solution is very sensitive to chloride ions, so you must pay attention to water washing before chromium plating.
4. Analysis and treatment of common abnormalities in photochromic:
1. Burnt:
a. The current density is too large;
b. Nickel layer passivation;
c. False burning: too much light nickel additive;
d. The product structure is complex and requires special hangers or pictographic anodes;
e. The trivalent chromium content is too low or too high;
f. The influence of impurities (especially the influence of nitrate radicals);
g. The solubility of the plating solution is abnormal.
2. Poor deep plating ability, no chromium on low areas/recesses (yellowing):
a. The current density is too small;
b. The pH value of bare nickel is too high;
c. Excessive trivalent chromium content;
d. The sulfuric acid content is too high;
e. Anode abnormality;
f. Breakdown of the mounting position (the conductive effect of the mounting device is poor or the carrying current is too small, the coating in the low area is too thin, etc.);
g. Impact of impurities.
3. Poor bonding (peeling):
a. The hanging fixture has poor conductivity or secondary conductivity;
b. Caused by bipolar phenomena;
c. Coating passivation;
d. Organic pollution;
e. The water washing tank is abnormal.
4. Color development of coating:
a. The sulfuric acid content is too low;
b. The hanging fixture has poor electrical conductivity;
c. The current entering the tank is too small;
d. The temperature is too high.
5. The hanging mark is obvious or the hanging mark is black:
a. Abnormality before chrome plating;
b. The hanging point is too thick;
c. The concentration of the plating solution is too low.
6. Salt spray test performance NG:
a. Sulfur pollution of semi-bright nickel or too small potential difference, etc.;
b. Organic pollution;
c. The nickel layer is too brittle;
d. Too much chromium plating current causes chromium micro-cracks.
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