Surface Treatment Before Oxidation


The influence of the material composition and purity of aluminum products on the quality of the aluminum oxide oxide film has long been understood by science and technology workers. However, in industrial production, the surface processing quality of China’s aluminum products sheet seriously affects the quality of anodized products, this contradiction is becoming increasingly prominent.

Surface Treatment Before Oxidation
Surface Treatment Before Oxidation

International aluminum parts are milled, smooth as a mirror, and have excellent quality after oxidation. In China, aluminum materials are often not very shiny, with bubbles, scratches, and rough skins. These defects are still exposed after anodizing oxidation. The decorative techniques such as various pattern printing and thermal transfer printing are especially serious due to poor quality and surface conditions of the board. Therefore, improving the appearance quality of the plate has become an important part to ensure the best quality of aluminum product oxidation.

In the degreasing treatment of aluminum products before oxidation, most factories still use weak alkali chemical degreasing.

Or caustic soda to remove oil and wash, but in recent years, more and more factories have adopted the method of adding surfactants to remove oil. Utilizing the unique physical and chemical properties of surfactants, reducing surface tension, emulsification, solubilization and foaming, and its own good chemical stability to alkali, hard water, etc., to improve the degreasing and purification effect and make the alkaline surface form a layer Foam layer, inhibits alkali mist from escaping, reduces pollution, and improves operating conditions. For example, Tianjin No. 3 Aluminum Products Factory introduced the use of AS anionic surfactants produced by Tianjin or Shanghai Synthetic Detergent Factory for aluminum basin whitening, and received good economic results. The specific process is caustic soda (NaOH) 10%; temperature 97 ~ 100 ° C; time 5 ~ 7 seconds. Surfactant AS is added in an amount of about 0.2 grams, depending on the situation.

In order to make the surface of aluminum products bright and smooth, the aluminum products after molding are generally mechanically polished. But after mechanical polishing and oxidation, only a smooth oxide film can be obtained, and the gloss is often not enough. For products that require high-gloss decorative oxide films, chemical polishing or electrolytic polishing is required after mechanical polishing. Pure or high-purity aluminum-magnesium alloys can obtain glossy surfaces with high reflection coefficients after chemical polishing or electrolytic polishing, especially electrolytic polishing, which can achieve very satisfactory results.

Unfortunately, the tri-acid chemical polishing solution generally contains “Huanglong” because it contains nitric acid (HNO3) and is heated to decompose nitrogen dioxide (NO2). The high quality and stable electrolytic polishing solution contains chromic anhydride, which results in chromium-containing wastewater, pollutes the environment, and causes three waste treatment problems. Naturally, people want to study the chemical polishing and chromium-free electrolytic polishing processes that do not produce “Huanglong”. “Yellow smoke-free chemical polishing additive WXP for aluminum parts” produced by PTJ Shop was approved with the assistance of Beijing Environmental Protection Department. Additive WXP is a brightening agent for phosphoric acid and sulfuric acid type polishing solutions, and has the function of inhibiting acid mist. The process formula used is phosphoric acid (specific gravity d = 1.7) industrial pure 800 ml; sulfuric acid (specific gravity d = 1.84)

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By William

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