- Mar 20, 2018 -
There is an interdependent relationship between cathode current density and temperature during the chrome plating process. When chrome plating is performed in the same solution, a chrome plated layer having three different properties of bright chrome, hard chrome, and white chrome can be obtained by adjusting the temperature and current density and controlling it in an appropriate range, as shown in FIG. 4-20. In the area of low temperature and high current density, the chrome coating is dark gray or burnt. This kind of coating has reticular cracks, high hardness, and high brittleness. In the area of high temperature and low current density, the chromium layer is milky white. This kind of organization is delicate and there are few pores. Cracks, good protection performance, but low hardness, poor wear resistance; medium temperature current density or a good combination of the two, you can get a bright chromium plating layer, this chromium layer is high hardness, fine and dense mesh cracks .
When the current density is constant, the current efficiency decreases as the temperature increases; if the temperature is fixed, the current efficiency increases as the current density increases. However, when the ratio of chromic anhydride to sulfate ions decreases, the change becomes smaller. Therefore, in the case of hard chrome plating, under the premise of satisfying the plating performance, a lower temperature and a higher cathode current density are generally used to obtain a higher plating deposition rate. When the temperature is constant, the dispersibility of the plating solution is slightly improved with the increase of the current density. Contrary to this, the current density is constant, and the dispersibility of the plating solution decreases to a certain degree with the increase of the plating solution temperature. The production of medium-temperature (45 ~ 60 °C) and medium current density (30 ~ 45A/dm2) is generally used to obtain bright and hard chromium plating. Although the plating process for bright plating is quite wide, considering that the dispersibility of the chromium plating solution is particularly poor, it is necessary to strictly control the chromium plating layer with uniform thickness in different parts when plating complex or hard chromium. Temperature and current density. When the chrome plating process conditions are determined, the temperature change of the bath is preferably controlled between the soil (1 to 2) °C.