Strengthen chromium solution management (composition and configuration of chromium solution)

Ensuring the correct and stable concentration ratio of the chromium bath solution is an important step in obtaining a compact chrome layer and improving the quality of the chrome layer. Therefore, it is essential to ensure that the various chemical components of the chromium solution are pure and that the ratios are precise.

(1) Composition of the chromium plating solution

The basic components of the chromium plating solution arechromic anhydrideand sulfuric acid, which can be divided into three concentrations: low, medium, and high, based on the concentration of chromic anhydride. The chromium plating used for gravure printing adopts a medium concentration chromium solution, specifically a plating solution with a chromic anhydride concentration of 180–250g/L. A plating solution with a chromic anhydride content of 250g/L and a sulfate content of 2.5g/L is called standard chromium plating solution, which is commonly used for hard chrome plating. The composition of chromium solutions used by most plating companies is as follows:

(a) Chromic anhydride (CrO₃), with a content of 190–250g/L.

(b) Sulfuric acid (H₂SO₄), with a content of 1.9–2.5g/L. The ratio of chromic anhydride to sulfuric acid is: CrO₃:H₂SO₄=100:1. Under different actual production conditions, the ratio may fluctuate between 100:(0.8–1.2). The relationship between chromic anhydride content and Baume degree is shown in the table below.

(2) Preparation of the chromium plating solution

(a) Place the calculated amount of chromic anhydride into the tank, add two-thirds of the total volume of deionized water, heat to 50–60°C, and stir the solution while heating, then dilute to the total volume. Since industrial-grade chromic anhydride contains about 0.4% sulfate, samples should be analyzed before adding chemically pure sulfuric acid to meet process specifications, and stir evenly.

(b) During the chromium plating process, the cathodic reaction is as follows:

 2H⁺+2e→H₂↑

Cr₂O₇^2- +8H⁺+6e→Cr₂O₃+4H₂O

(c) The raw materials used to prepare the chromium solution must be pure, and each batch of materials must be stable. Some companies have difficulty identifying problems due to impure and unstable raw materials. It is recommended to choose high-quality electroplating-grade chromic anhydride from MaiTuo, which has the following advantages:chromic anhydride1. High purity and low inorganic impurity content, ensuring the quality of the chrome plating;

2. Organic impurities are far lower than similar products, ensuring the long-term use of the plating solution;

3. The highest quality chromic anhydride internationally, enhancing the market visibility of users and increasing customer confidence in product quality and stability.

MaiTuo