Because of its unique color, good decoration and ornamental properties, the black coating has always been favored by consumers and is widely used in the industries of instrument and meter parts, electronic and electrical products, and optical instruments. Based on the requirements of environmental protection, the electroplating process of trivalent chromium plating solution has been rapidly popularized from 2004 to 2006. With the maturity of the process technology, it has gradually replaced the electroplating process of hexavalent chromium plating solution. However, the black chromium plating process of trivalent chromium plating solution may be due to the lag of market demand and application technology. It did not appear strong market demand until 2008, and there has been a trend of gradual popularization in recent years, but related reports are Very few.
1. Classification of black chrome plating
Black chromium coatings on the market can be roughly divided into two types: yellowish-black and bluish-black. This may be due to the earlier launch in the market. Currently, the yellowish-black coating is still the main type. For example, Dazhi Chemical's 330 series, Mai Demei's 118230 series and Ruiqi Chemical's RTC-471 series; and the blue and black products mainly include Ruiqi Chemical's RTC-481 series, Tianze Technology's Cr-3004 series and Shangma Technology's BTC series. From the comparison of the color depth of the coating, the blue-black type is generally darker than the yellow-black type. The above products basically include various colors required by the market, and you can choose a suitable product according to your needs.
If divided by the solution system, it can be divided into two types: sulfate type and chloride type. Among the above-mentioned products, Ruiqi Chemical and Mai Demei's products are sulfate type, and the rest are chloride type.
2. Advantages and disadvantages of black chrome plating
In practical applications, the w(Cr) in the black chromium coating obtained from the trivalent chromium plating solution is between 50% and 80%. The content of other metals and non-metals in the coating is relatively high, and it does not have the self-passivation effect of the white chromium coating. , Belongs to the anodic coating, its surface hardness is only 300～500HV, which is much lower than the white chromium coating (700HV), so it has certain limitations in the application of metal electroplating. At present, it is mainly used in plastic electroplating, which is to a certain extent The above limits the promotion of black chromium electroplating with trivalent chromium plating solution.
Black chromium electroplating in trivalent chromium bath also has some advantages that are temporarily difficult to compare with white chromium electroplating. Taking the sulfate type electroplating process as an example, it has fast deposition speed, sustainable thickening, solution movement performance, and coating uniformity with electroplating time. Increase and improve; the tolerance of metal impurities is high, and there is no need for frequent electrolytic impurity removal treatment, etc., which has a better foundation for the promotion of electroplating black chromium than electroplating white chromium.
