以氯离子为催化剂的镀锌低铬彩钝试验

Test of low-chromium iridescent passivation with chloride ion as catalyst

采用以邻氯苯甲醛作主光剂的氯化钾镀锌液,在250mL赫尔槽中以1A电流对钢试片镀5min,经2%(质量分数)稀硝酸出光并水洗后进行低铬彩钝。于冬天室温9°C时在含铬酸酐5g/L的基础钝化液中逐渐加入KCl。当KCl含量低于10g/L时,吹干后的钝化膜附着力好,但发雾严重;当KCl含量达到20g/L时,搅拌状态下镀得的试片在钝化后完全不发雾。加热试验表明,25°C为最佳钝化液温,可在宽电流密度范围内获得正看与侧看均以色泽浓鲜、偏红且附着力良好的彩钝层。

Hull cell test was conducted using steel sheet as substrate in a 250 mL of potassium zinc plating bath with o-chlorobenzaldehyde as primary brightener at 1 A for 5 rain. The zinc coatings obtained were treated by low-Cr iridescent passivation after etching in 2wt% dilute HNO3 solution and rinsing. KC1 was gradually added to the passivation bath comprising 5 g/L CrO3 at room temperature （9 ℃ in winter）. The blow-dried passivation film has good adhesion strength but looks hazy when the KC1 content is 〈10 g/L. The passivation film on the zinc coating electroplated under agitation is totally clear without haze when the KC1 content is up to 20 g/L. The results of heating test showed that the optimal passivation temperature is 25 ℃, at which the iridescent passivation films on the zinc coatings prepared in a wide range of current density have strong reddish color in both frontal and oblique views and good adhesion strength.