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Alkaline degreasing agent
Release Date:2016-7-15 Source:xiashundong Views:945
Alkaline degreasing plating pretreatment skim the most commonly used procedure, the main characteristics of a degreasing agent non-toxic, cheap, degreasing effect is good, and easy to manage, the equipment is simple, it can be said alkaline degreasing both cheap and good management, therefore widely used. Its principle is degreasing solution by means of saponification and emulsification, to remove two types of oil purposes. The so-called saponification, that is, oil and degreasing agent with a base chemical reaction process soap.

Alkaline degreasing agent consisting of:
In an aqueous solution of alkaline cleaner based on animal fat to make it water-soluble soaps by saponification. This soap surfactant, non-polar mineral oil emulsification, making it "solubilization" in the aqueous phase aqueous alkaline cleaning agents can be dissolved sweat and other inorganic contaminants, it is also able to wash their go with. Added synthetic detergent cleaning solution. Cleaning action of the oil more efficiently. Alkaline chemical solution to clean all kinds of dirt, especially suitable for the next step requires a hydrophilic surface. It has a relatively economical solvent cleaning liquid can be washed with water. There are non-flammable, non-toxic. General aqueous alkaline solution as good as organic solvent cleaning fast and require heating, but also with a mechanical stirrer, and the need to pay attention to the corrosive effects of high pH on copper, aluminum, zinc and other metals.
Now with the development of technology. It appeared surfactant, which can be used with an alkaline aqueous solution. Maintaining both the advantages of an alkaline degreasing agent inexpensive and convenient, but also greatly improve the efficiency of degreasing, degreasing temperature decrease, compared with the surfactant alone, i.e., reduced costs degreasing, degreasing effect but also high. Therefore, the current is widely used on the pretreatment process. Alkaline degreasing agent also has disadvantages associated with: 1) require rinsing; short 2) plating bath life; 3) high energy consumption; 4) the need to neutralize the acid; 5) I need to de-oil treatment; 6) require further processing.

1) Sodium hydroxide (NaOH): Sodium hydroxide is a strong base, with a strong saponification. Oils (e.g., monostearate) does not dissolve in water, but after saponification, they are in the form of soap dissolved in water and glycerol. That move, vegetable oil skimmed principle.
C3H5 (C17H35COO) 3 + 3NaOH = 3C17H35COONa + C3H5 (OH) 3
2) sodium (Na + C0 + · nH2O): choice of 10 water or anhydrous salts. Effect of saponification both are weak, but it can play a slow wetting and dispersing fat role. Sodium carbonate and sodium bicarbonate (Na2CO3 · NaHC03 · 2H2O) and sodium carbonate complex salts have the same effect, and it does not damage the base metal, for cleaning non-ferrous metals are safe.
3) is a chemical combination of sodium silicate and SiO2 Na20:
Sodium orthosilicate (2Na20 · SiO2 · nH20) SiO2 / Na20 = 0.5
Sesqui sodium silicate (1.5Na20 · SiO2 · nH20) Si02 / Na20 = 0.667
Sodium (Na20 · SiO2 · nH20) SiO2 / Na20 = 1.0
A sodium silicate (Na20 · 2SiO2 · nH20) SiO2 / Na2O = 2
Two sodium (Na20 · 3SiO2 · nH20) SiO2 / Na20 = 3
When using silicate used in degreasing to clean, can not leave the metal silicate surface, otherwise the next step would silica gel acid adsorbed on the surface, it is difficult to remove, resulting in hair spray coating and the substrate and the influence coating adhesion.
4) sodium phosphate
Dodecahydrate, sodium metaphosphate, sodium tripolyphosphate and other commonly used during cleaning. Sodium phosphate penetration, wetting and other aspects of the role of the second son of sodium silicate, but not strongly react with the metal, its aluminum, zinc and other less severe corrosion, but it also can be the base metal against corrosion, and We have hard water softening.
5) water softener
Soften hard water additives, that is, we often say that the washing aid. As we all know, animal fats may be formed in alkaline water-soluble long-chain fatty acid sodium (sodium soap) after hydrolysis. Although sodium soap soluble in water, but containing Ca2 +, Mg2 + hard water will form a water-insoluble long-chain fatty acids, calcium or magnesium salt (known as calcium or magnesium soap soap). In addition, Ca2 +, Mg2 + also insoluble compounds with alkali degreasing liquid C032-, 0H-, PO43-, Si032- like.
The insoluble material is easily attached to the surface of the plating, the coating glitches, pinholes, rough and poor adhesion. In alkaline degreasing agent must be added to make the water softening additive, also known as a softener. Some are with Ca2 +, Mg2 + chelator formation of soluble chelates can be suppressed Ca2 +, Mg2 + and other metal ions to form a precipitate, can eliminate the water insoluble lumps, so that it changes the suspension is dispersed into the solution.

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