Metal surface passivation treatment

Passivation of stainless steel is on the steel surface and welding plating a layer of chromic oxide film, thus improve the corrosion resistance of stainless steel. Passivation is an effective way to decontamination. For example, the metal surface and weld deposit of iron particles can be this way to get rid of ( These iron particles are often due to cutting, shaping, friction or metal brushes, etc) which is formed by the role of 。 Before passivation pickling can remove all of the pollutants, and can selectively remove metal surface corrosion area of the smaller. In order to effective pickling and passivation, in prior to pickling passivation must get rid of all the organic dirt, grease, etc. As A result, the commonly used operation steps are as follows: A, pre-cleaning/except oil, an acid cleaning C, D, B secondary cleaning, passivation/decontamination E F, final cleaning and drying, normally use plating products should be as far as possible. For small products or pipe fittings, shall be preferred by immersed in the bath. Small area, Weld, repair) , or when plating for some products ( For example, has installed the surface of the tubular heat exchanger) Bad time, it is best to use paste processing. Production workshop shall establish a written document according to this manual. And the documents submitted to the buyer in writing and give confirmation. Note: passivation not contain any hydrochloride, or even any chloride. At low temperature in pickling passivation may fail, so the pickling passivation treatment shall be in a high enough stainless steel pickling passivation processing technical specification (at room temperature ＞10℃） 。 In any case because when under the guidance of the supplier for processing. During the processing of used water ( Such as bath, diluent, cleaning fluid, etc. ) Should be handled to ensure low chloride content ( Theoretical maximum chloride content of 30 PPM) 。 Copper passivation the standard potential of copper is, is the dry atmosphere without obvious structure corrosion phenomenon; Once in the humid environment and industrial atmosphere is easy to rust. Copper after heavy chromate passivation; To obtain a very thin layer of acid salt membrane layer, can improve the copper in damp environment and industrial atmospheric corrosion resistance of passivation film color as the material and craft different and different, have certain adornment sex, after chromate passivation membrane layer metal grey in color. Facilitate the tin soldering after chromate passivation. Copper passivation process is as follows: the former passive acceptance to organic solvent degreasing, hang - chemical degreasing or electrochemical flow in addition to the oil to flow of hot water to wash, wash in cold water to pre corrosion, the flow of cold water to wash - light corrosion - the flow of cold water to wash - weak corrosion - flow wash in cold water flow to chemical passivation, wash in cold water and cold water wash, stable processing ( According to the need for) To dry, remove to test film quality when the copper and copper alloy in a certain proportion of chromic acid and chromic acid solution, under the action of solution, also will be generated by alkali type of chromate and hydrate layer, to protect the copper and copper alloy. Instrument in the elastic element of beryllium bronze often requires the passivation of copper processing, in order to improve the protective ability. The process is roughly as follows; First of all, beryllium bronze components should be to oil, to rust. After degreasing, at 80 ℃ for 10 ~ 15% of dilute sulphuric acid pickling, about 20 minutes, to remove the oxidation corrosion layer, then can be directly to the passivation of copper, can also be the first bright pickling ( General precision components without) After the passivation of copper. Bright pickling time is very short, about 10 seconds, and then take out immediately wash with water, into the passivation solution and formula for passivation solution: passivation time for 30 seconds, and finally wash with water and dry, when necessary, in blow dry before the alcohol to clean it again. Copper passivation although has certain protective ability, but under the condition of damp and hot, is not resistant to corrosion. Therefore, to use in hot and humid conditions after the passivation of copper, seal protection measures should be taken. Passivation of aluminum alloy in before spot welding, the need for passivation of aluminum alloy. After passivation treatment of passivation film, also known as chemical conversion coating, generally in our country also known as aluminum alloy modification of passivation film. Why passivation treatment? This is because, without passivation of aluminum alloy surface resistance, in a few hours, will soon rise, and after passivation treatment of aluminum alloy, form a layer of passivation film, the passivation film is not only conducive to the stability of the spot welding of low surface resistance, and porosity. Because of the passivation film is very thin, so the need for close processing. In addition, the passivation layer under the temperature of 100 ~ 120 ℃ after baking, can make the paint ( Especially the lacquer that bake) The bottom of the good. This to improve the adhesion ability of paint or lacquer that bake is extremely beneficial. Passivation film was able to bite on reason, or paint is not due to the adsorption film itself, but rather caused by inertia of passivation film. Passivation film, in fact, although it is porous, pore is too small, but the film is very thin, larger particles cannot be well into film. But because it is inert, the underlying reason is still a good paint. Another major advantage of the passivation of aluminum alloy is, after the failure of paint or spray paint layer, the passivation treatment of aluminium alloy can still prevent the expansion of the corrosion, thus to metal can be protective, besides the above-mentioned purposes, are now in the electronic computer, typewriter, and all kinds of electrical products are widely used. Aluminum passivation treatment process is simple, does not need to do complicated pretreatment work, also don't need to do hang ( Using the basket can be mass production) , more do not need to dc power supply and other auxiliary equipment, and the processing time is short, high production efficiency, the application of chemical raw materials is more economic. Passivation of aluminum alloy main process is as follows: the organic oil removal - chemical degreasing - light to passivation treatment, drying and leaching