Metal workpiece welding process, before welding cleaning treatment is very important, for different metal workpiece material, the welding process requirements are different, the need to choose different metal workpiece cleaning agent, the general market hardware material is divided into steel, carbon steel, alloy steel, cast iron and so on. According to different shape and Application different, its cleaning The process method is also different, but the cleaning agent for hardware work can be the same. Below, Dongguan Mingkang industry and according to the response of many years customer, summed up the common process and method of cleaning hardware workpiece.
Cleaning process before welding
1. Cleaning process before steel welding
1. The most widely used cleaning treatment for soft steel before welding is sandblasting, and the best welding intensity is sand blasting.
2. Before stainless steel is cleaned before welding, stainless steel is the only steel in all steel materials that has higher welding strength after acid etching. The commonly used etching methods are dichromic acid oxidation treatment, water vapor jet cleaning aggravated chromic acid treatment, nitric acid mixed acid oxidation, nitric acid hydrofluoric acid mixed solution after oxidation treatment of dichromic acid passivation treatment.
Two. Cleaning process before painting
Iron and steel should be treated with degreasing and rust removal before spraying, and phosphate treatment should be carried out to form a phosphate protection film on the surface of the washed steel to prevent rust.
The typical process of cleaning steel before painting is impregnation. It includes the following processes:
Degreasing, washing, rust removing, water washing, surface dressing, phosphating, film forming, washing, post-treatment and drying.
Three. Cleaning of oil pressure pipeline
When installing the oil pressure device, the pipeline must be adequately pickled. Before the liquid bath is pickled, remove the dirt from the pipes with significant corrosion or bonding with the wire brush. The application of paint film on the inner wall of the pipe is stripped and pickled. Degreasing and cleaning should be carried out for pipes with antirust oil or grease. Acid washing was carried out by acid washing, water washing, neutralization and washing. Acid pickling is usually carried out at room temperature with a 5% hydrochloric acid solution containing a corrosion inhibitor. The pipe can be cleaned after cleaning the pickling tank, and can also be cleaned by acid circulation after assembling the pipeline. It is more efficient to use the pump to circulate the acid in the pipeline after the pipe is assembled. The process is to clean 3H with 5% hydrochloric acid at normal temperature, rinse the acid with water, and then neutralize 2H with 0.5% sodium hydroxide or sodium carbonate solution, and then wash the water fully.
Four. Degreasing, rust removing and rust prevention “three in one” cleaning.
In common use of carbon steel pipes, reaction towers, storage tanks, heat exchangers, heating furnaces, sealed tanks and other equipment, or complete sets of industrial equipment, chemical cleaning treatment, such as oil removal, descaling, rust removal and passivation, should be carried out before and during the operation to improve the purity of the product to avoid catalytic agent poisoning and to improve heat exchange efficiency of heat exchange equipment. Reduce energy consumption and cooling water consumption. At present, the typical cleaning processes used in complete sets or equipment are: degreasing cleaning, discharge (waste liquid treatment), water rinsing, acid washing, discharge (waste liquid treatment), water rinsing, rinsing (citric acid treatment), neutralization (ammonia treatment), antirust treatment (passivation), discharge (waste liquid treatment) and end.
Traditional basic substances (three sodium phosphate, sodium hydroxide, sodium carbonate, etc.) are used to remove oil and degrease, and then carry out acid cleaning and rust removal (hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, citric acid, etc.), and then passivate under alkaline conditions. An oil removal, rust removal and antirust “three in one” cleaning agent with phosphoric acid as the main agent can be used in the new equipment (such as pipes and tanks) to finish the process of removing oil, rust and rust. Compared with the traditional cleaning process, the cleaning process can be greatly shortened and the discharge amount of 4/5 washing wastewater can be reduced.
The main ingredients of the “three in one” cleaning agent are phosphoric acid, phosphoric acid, two hydrogen zinc, tartaric acid or citric acid, surfactant, film accelerating agent, etc. The inhibitor used in conjunction with the “three in one” detergent is alkaline, so it should be added temporarily.
1, “three in one” cleaning and rust prevention principle
The main function of cleaning and rust removing in the “three in one” cleaning agent is the phosphoric acid.
(2) the protective effect of film forming under acidic condition is that phosphates, such as two hydrogen and zinc phosphate, can form protective films. The “three in one” antirust effect is mainly reflected in the formation of a dense phosphating film on the metal surface after cleaning and rust removal.
In order to accelerate the formation of the passivation film, the film promoter is added. The role of the film promoter is to make use of its synergistic effect to increase the micro cathode area, accelerate the rapid oxidation of hydrogen evolution and promote the formation of the membrane.
Iron ion masking agents such as tartaric acid or citric acid, such as tartaric acid or citric acid, can play a complex role in the iron ions in the solution. The iron ions, which are rapidly elevated in the solution, are controlled in a certain concentration, avoiding the excessive iron ion concentration, which can catalyze the corrosion of the metal and promote the rust removal and film formation. The synergy of each other.
The effect of surfactants is to reduce the cleaning step and make the “three in one” cleaning also have the function of removing oil at the same time. The addition of surfactants can not only improve the emulsification, wetting, infiltration, dispersion and solubilization of a small amount of oil, but also improve the uniformity and corrosion resistance of the film, and improve the surface cleanness. Therefore, it is possible to avoid the occurrence of dust or whitening on the metal surface after cleaning. Surfactant is the preferred nonionic surfactant.
The study showed that the formula was 25% to 30% phosphoric acid
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