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QRD–82 HIGH SPEED DECORATIVE CHROMIUM PLATING PROCESS
■Adopt solubility and mixed catalyst, easy to operate.
■It has higher current efficiency of cathode and deposition velocity, can operate under high current density.
■The components can be activated well with wide brightening range.
■Tolerance against impurities.
■Excellent covering power and dispersive ability.
2. Bath Composition and Working Conditions
Bath composition & Technical Data
Standard Usable Range
150 – 350
Purity sulfuric acid（density=1.84g/L ）
1.2 g/L（ 0.65ml/L ）
0.75 –1.75 g/L （0.41~0.95 ml/L ）
Ratio ofCrO3 and H2SO4（CrO3 / SO4）：
125 ~ 250 : 1
QRD-82 make up solution ：
Proportion of bath（Bé ）
35 – 52
Plating tank: plastic tank or steel tank with liner PVC.
Rectifier: to have sufficient capacity to match bath facilities, ripple coefficient less than 5%, voltage not less than 15V.
Anode: use lead tin alloy (Sn: 4 ~ 7%) or lead antimony alloy as anode,
the cathode area: the anode area = 1: 2~3 (at work).
Heater: select titanium, lead or Teflon material.
Cooling pipe: selection of titanium or lead material.
4． Make Up the Solution
¨ Add two third（2/3） of deionized water into complete clean bath, heat the water until to 50℃.
¨ Add chromium trioxide with mixing to make it dissolved, add required HN-82 make up solution.
¨ Add water to required volume, adjust working temperature and mix it to make the bath uniform.
¨ Analyze the sulfate radical content, supply sulfate radical to prescriptive quantity by adding Purity sulfuric acid.
¨ Put the anode into the tank, and put dummy cathode to electrolyze with 6V volute for several hours, then start to operate plating.
5． Function of raw material
uChromium trioxide: Chromium trioxide is necessary component in the bath. When the concentration of chromium trioxide increases, the conductivity of bath will increase and the cathodic current efficiency will decrease. When chromium content is insufficient; the workpiece is easy to burn at high current area.
uSulfuric acid: Chromium plating solution must contain a certain amount of sulphate ion to reduce hexavalent chromium to chromium metal. Maintain the ratio of 200: 1 (chromic acid / sulfuric acid). If the proportion is high(sulfuric acid is insufficient), it will reduce the deposition rate and gloss of the plating layer. Black stripes and brown chrome stains will appear. If the proportion is low (too much sulfuric acid), it will slightly improve the luster of the plating layer, but also reduce the cathode current efficiency and lower deposition rate and depth of capabilities. If the sulfuric acid content in the bath solution is too high, barium carbonate can be used to precipitate redundant sulfuric acid. 2 grams of barium carbonate precipitates 1 gram of sulfuric acid.
udeposition rate and gloss of the plating layer. Black stripes and brown chrome stains will appear. If the proportion is low (too much sulfuric acid), it will slightly improve the luster of the plating layer, but also reduce the cathode current efficiency and lower deposition rate and depth of capabilities. If the sulfuric acid content in the bath solution is too high, barium carbonate can be used to precipitate redundant sulfuric acid. 2 grams of barium carbonate precipitates 1 gram of sulfuric acid.
uTrivalent chromium: After new bath solution being electrolyzed, trivalent
chromium will appear. Its content is generally from 0.5 to 2g/L. When trivalent chromium is too low, the deposition rate will be slow; plating layer will be soft with poor throwing power. When trivalent chromium is too high, bright area of plating layer and the conductivity of the solution will be reduced. The concentration of trivalent chromium is affected by the area ratio of the anode and cathode. Electrolysis with small cathode area and big anode area can reduce redundant trivalent chromium, otherwise, can increase the the concentration of trivalent chromium. Generally, the ratio of anode and cathode area is 1.5:1 to 1:1.
6． Replenish Additive
QRD-82 make up solution is added when open cylinder and transfer cylinder. But it could be consumed during the plating process and being brought out by work pieces. When its content is insufficient, bright area will get narrow, throwing power will decrease. So it can be supplemented slightly according to production. Generally, just add QRD-83 as replenishers. Every 100KG of chromic acid, add 4~5 liters of QRD-83 replenishers.