Energy-saving and environment-friendly novel process for stainless steel passivation

Abstract

The invention relates to an energy-saving and environment-friendly novel process for stainless steel passivation. An adopted passivator contains the ingredients in percentage by mass: 20-50% of polybasic weak acid, 10-30% of catalysis promoter, 0-5% of thickener and the balance of water. The process comprises the specific process flows: (1) coating through brushing or mopping, drying through wiping, ageing, naturally drying or baking, and inspecting; or (2) coating through dipping or spraying, drying through dripping, ageing, cleaning or drying through wiping, naturally drying or baking, and inspecting. According to the process, toxic and harmful ingredients, such as chromate, hydrofluoric acid, sulfuric acid and nitric acid, are abolished fundamentally, and a polybasic weak acid and catalysis promoter technology is adopted, so that the process is completely non-toxic and harmless, is free from environmental pollution, is moderate in odor and is beneficial to health; the requirements on high corrosion resistance and high integrity can be met by the passivating depth of only 20 microns, so that the mechanical and physical properties of stainless steel are better protected from being affected by passivating corrosion. According to the process, washing is required or not, and then, water is saved by over 80%, so that the process is worthy of being popularized and applied to the stainless steel passivation in the fields of food, medical treatment, aviation, aerospace, nuclear power and the like.

Description

technical field [0001] The invention relates to a new technology of stainless steel passivation for energy saving and environmental protection, which belongs to the technical field of stainless steel. Background technique [0002] Stainless steel has good high temperature oxidation performance, good low temperature performance and excellent mechanical and processing performance. Therefore, it is widely used in chemical industry, petroleum, power, nuclear engineering, aerospace, ocean, medicine, and light industry as passivation film. If the film is incomplete or defective, stainless steel will still be corroded. In engineering, pickling and passivation treatment is usually carried out to maximize the corrosion resistance potential of stainless steel. Surface oil, rust, non-metallic dirt, low-melting-point metal pollutants, paint, welding slag, and spatter are brought during the stainless steel process. These substances affect the surface quality of stainless steel equipmen...

AI Technical Summary

Problems solved by technology

After pickling, an average layer of 10 μm thick on the surface of stainless steel is corroded. The chemical activity of the acid solution makes the dissolution rate of the defective part higher than that of other parts on the surface. The oxides of chromium are preferentially dissolved than chromium and chromium oxides, and the chromium-poor layer is removed, resulting in the enrichment of chromium on the surface of stainless steel. This chromium-rich passivation treatment will also affect the composition and structure of the film, thus affecting the stainless property

[0003] The stainless steel industry is developing rapidly at home and abroad, but the pickling passivation technology and process of stainless steel are seriously lagging behind, and the traditional nitric acid, hydrofluoric acid, chromate passivation, or nitric acid, sulfuric acid, hydrofluoric acid, chromic acid passivation are still used. This technology and process is highly toxic, smells smoky, consumes energy and water, seriously pollutes the environment, and poisons people's health

In recent years, although there are also patents, there are no breakthrough technological achievements. At best, it is to reduce toxic components, such as low chromium passivation, or abandon hydrofluoric acid, or trivalent chromium passivation, etc., but they cannot fundamentally solve the problem. The problem of polluting the environment even affects the quality of passivation, so it is rarely used

In the past two years, stainless steel environmental protection passivation solution has also appeared on the market, but it has little passivation effect; the United States has also introduced a citric acid environmental protection passivation solution, which has entered the domestic market, but the use conditions are relatively strict, and it needs to be removed. Repeated cleaning with ionized water