Sensitization treatment: Sensitization refers to the adsorption of a layer of reducing agent on the surface of coarsened hydrophilic plastic, letting it absorb a thin layer of metal and perform as the catalytic center of auto-catalytic plating through reduction reaction in the activation treatment.
敏化过程的反应机理是塑料敏化处理后，在其表面吸附有一层敏化液，进行清水冲洗时，因为清洗水的pH 值高于敏化液的pH 值，发生两价锡的水解作用。
The reaction mechanism of sensitization process is that after the sensitization treatment of the plastic, there is a layer of sensitizing solution adsorbed on its surface. When washing with water, the Sn(II) hydrolyzes because the pH value of the water is higher than that of the sensitizing solution.
Activation treatment: Activation is to use the solution of catalytic active metal compounds to react with the sensitized surface, so that metal ions can be reduced to metal, forming a catalytic center on the surface of the plastic as the crystallization core of the deposition coating.
还原：为了除尽试片表面的活化剂（Ag+或Pd+2），防止将它们带入镀液中，导致镀液提前分解而失效，所以应进行还原处理。此外，还原还可以提高催化层的活性，从而加快化学沉积速度。还原液采用甲醛 [HCHO, 36-40%] : 水=1:9，在室温下反应30s。
Reduction: In order to eliminate the activating agents (Ag+ or Pd2+) on the surface of the plastic, preventing them from being brought into the plating solution and decompose it in advance, making it invalid, the reduction treatment is needed to be carried out. In addition, reduction can also improve the activity of catalytic layer, thus accelerating the rate of chemical deposition. The reducing solution is a mixture of 1 part of 36-40% methanal and 9 parts of water, reacting under room temperature for 30 seconds.