In recent years, metal surface treatment technology has developed rapidly and has been widely used in many fields. Pretreatment plays a very important role in surface treatment technology and engineering. It is not only indispensable as a "pretreatment process" before surface treatment, but also closely related to the success or failure of subsequent surface treatment.

Matrix pretreatment such as degreasing, derusting, phosphating and rust prevention is prepared for metal coating technology and metal protection technology. The quality of matrix pretreatment has a great impact on the preparation of coating and the use of metal. For example, the salt spray test of the same coating with and without phosphating treatment results in a difference of about twice the corrosion resistance. It can be seen that pretreatment such as oil removal, rust removal, rust prevention and phosphating plays a vital role in the rust prevention ability of the coating and the protection ability of the metal.

The purpose of substrate pretreatment: first, to increase the bonding strength between the coating and the substrate, so as to increase the adhesion; second, to increase the functions of the coating, such as anti-corrosion, anti-wear and lubrication.

1. Inevitability of steel surface pretreatment process:

In the process of rolling or application, there are different degrees of impurities such as grease, scale or rust on the surface of steel. Before processing and coating, it needs to be eliminated, and then it can be sold as a commodity. If not, it will seriously affect the appearance quality and service life of the product and lose the competitiveness of the product. If the steel surface is coated without treatment, the oxide scale, rust or grease in the coating will be covered by the coating, and the coating will fall off soon, so that the sold products show a rusty appearance and lose the competitiveness of the products in the market. Therefore, the inevitability of pretreatment of steel surface has attracted great attention of the majority of enterprises.

1. Degreasing treatment of steel surface:

We know that the commonly used oil removal methods include solvent oil removal, electrochemical oil removal, chemical oil removal, surfactant oil removal, manual oil removal and mechanical oil removal. Different degreasing methods have different degreasing characteristics. Solvent degreasing is to use the structural similarity between organic solvent and oil stain to dissolve the oil stain in organic solvent to achieve the purpose of degreasing; Electrochemical oil removal generally takes dilute alkali solution as electrolyte and workpiece as electrode for electrolytic treatment. The gas precipitated on the electrode surface during electrolysis is used to forcibly separate the oil from the workpiece surface; Chemical oil removal is to remove oil by saponification reaction between alkali and oil; Surfactant oil removal uses its emulsification, solubilization, wetting and dispersion to achieve the purpose of oil removal. Mechanical and manual degreasing is self-evident.

In modern oil removal technology, the synergy of several substances is often used to achieve the best oil removal effect.

It is suitable for degreasing and cleaning of cast iron products before electroplating, blackening, phosphating and metal processing.           

2. Derusting treatment of steel surface:

During the processing of iron and steel products, the oxide scale and rust on the surface must be chemically cleaned to expose the iron and steel substrate, this will more effectively improve the treatment effects of electroplating, phosphating, oxidation (black and blue), stretching, calendering, rolling and rust prevention.

The most commonly used method of chemical derusting is hydrochloric acid derusting. Because hydrochloric acid derusting is fast and can be carried out at room temperature, it is widely used. However, in practice, there are "over corrosion" and "hydrogen embrittlement" in hydrochloric acid derusting, resulting in a large amount of acid mist, resulting in environmental pollution and social hazards.

The rust removal additive is mixed with hydrochloric acid and has the following characteristics:

Under normal temperature, the derusting speed is fast and the derusting effect is good;

It has the functions of penetrating, dissolving, dispersing and stripping oxide scale and rust;

The quality is good. The derusting quality meets or exceeds the Swedish derusting standard; SA class III and Germany BE class;

Good corrosion and fog inhibition effect: Due to the synergistic effect of various additives in the solvent, there will be no over corrosion and hydrogen embrittlement in the derusting process of iron and steel. The acid mist standard is less than the concentration specified by the state, which is conducive to the post-treatment of derusting;

3. Phosphating treatment of steel surface:

Phosphating overview:

Phosphating is a commonly used pretreatment technology. In principle, it should belong to chemical conversion film treatment. Phosphating on the surface of iron and steel parts is its main application in engineering, but phosphating can also be applied to non-ferrous metals such as aluminum and zinc parts.

Phosphating principle:

The process in which the workpiece (steel or aluminum or zinc) is immersed in phosphating solution (some acid phosphate based solution) and forms a crystalline phosphate conversion film insoluble in water on the surface is called phosphating.

The method of putting metal into phosphate solution containing manganese, iron and zinc for chemical treatment to form a phosphate protective film insoluble in water on the metal surface is called metal phosphate treatment. The phosphating film is of microporous structure, firmly combined with the matrix, and has good adsorption, lubricity, corrosion resistance, non adhesion to molten metals (SN, Al, Zn) and high electrical insulation.

According to the treatment temperature: high temperature type (75 ~ 100 ° C), high energy consumption, more phosphide deposition and the thickness of  formed phosphating film is up to 10 ~ 30g / m²), medium temperature type (50 ~ 75 ° C, treatment time is 5 ~ 15min, phosphating film thickness is up to 1 ~ 8g / m²), low temperature type (30 ~ 50 ° C) and normal temperature type (10 ~ 30 ° C), saving energy, easy to use. In addition to oxidants, accelerators are also added, low energy consumption, but the solution formulating is complex, and the film thickness is up to 0.2 ~ 7g / m²).

According to the chemical composition of phosphating solution: it is divided into Zinc series phosphating、 zinc calcium series phosphating、 zinc nickel series phosphating、 iron series phosphating、 manganese series phosphating and composite phosphating etc.

According to the phosphating treatment method, it is divided into chemical phosphating and electrochemical phosphating.

According to the quality of phosphating film: it is divided into heavyweight (film weight above 7.5g / m²), secondary heavyweight (film weight 4.6 ~ 7.5g / m²), lightweight (film weight 1.1 ~ 4.5g / m²) and secondary lightweight (film weight 0.2 ~ 1 g / m²).

According to the construction method, it is divided into immersion phosphating, spray phosphating and brush phosphating.

Phosphating function and application:

Function of phosphating before coating: enhance the adhesion between coating film (such as coating) and workpiece, improve the corrosion resistance of workpiece surface after coating and improve decoration.

The function of non-coating phosphating: improve the wear resistance of the workpiece and make the workpiece lubricated in the machining process,after proper post-treatment, the wear resistance of the workpiece can be improved.

Phosphating application: phosphating film is mainly used as the bottom layer of coating, lubricating layer during metal cold processing, metal surface protective layer, insulation treatment of motor silicon steel sheet, anti sticking treatment of die casting mold etc. It is widely used in automobile、vessels、aerospace、 machinery manufacturing、 home appliances and other industrial production. Necessity of phosphating: the pretreatment process of steel surface coating refers to derosination  (degreasing)、, rust removal、 neutralization、 surface adjustment、 phosphating and passivation. However, due to the different conditions of the workpiece surface, the production process is also different. Some processes have no degreasing or derusting process, and some processes have no surface adjustment process, but phosphating process is absolutely indispensable.

In the process of coating treatment, if the grease, oxide scale and rust layer are not removed, phosphating treatment is not carried out, painting or electrostatic spraying are directly carried out, the coating on the steel surface will fall off and lose the significance of coating.

Based on the above reasons, normal temperature zinc calcium phosphating solution、 normal temperature iron phosphating solution (powder) and other products effectively meet the process requirements of normal temperature phosphating. This kind of phosphating products have stable performance, convenient operation, simple adjustment, normal temperature application, energy saving, less consumption, large treatment area, low cost, dense and uniform phosphating film, good adhesion and strong corrosion resistance.

Normal temperature iron phosphating: (simple phosphating)

Advantage:

1) Also known as color phosphating, it is suitable for manufacturers with low requirements for coating quality or limit by customer production conditions (less tank requirements).

2) In the process of use, it does not need frequent adjustment, does not contain nitrite, does not need frequent detection and testing, and is easy to operate and use.

3) The phosphating film formed belongs to iron phosphate phosphating film, the appearance is blue with color, the phosphating film is thin and dense, there is no dust, mark and white return on the surface, and the film itself is not brittle.

4) Less application tanks. (4~6 tanks)

5) This product has the advantages of less consumption, low cost, less consumption and large treatment area.

6) This product is non corrosive, non combustible, non explosive, easy to use, transportation and storage.

Shortcoming:

1) It is simple phosphating, and the film belongs to passive film

2) The appearance color of the film is unstable and presents a colorful series.

3) Thin film, weak adsorption and corrosion resistance.

4) It is difficult to adjust the working fluid. Once it is tired, the waste tank can only be reconfigured.

5) The market share is decreasing year by year.

4. Blackening treatment of steel surface

The traditional blackening method is alkaline oxidation blackening. Alkaline oxidation blackening usually uses high temperature and nitrite as oxidant to heat and oxidize iron and steel parts in extremely concentrated alkaline oxidation solution, so as to form a blue ~ Black Fe3O4 protective oxidation film on the surface of parts. Due to uneven heating and high temperature of the workpiece during blackening, the content of the solution changes rapidly, often resulting in uneven blackening film. Therefore, people are eager to seek room temperature blackening process to achieve the purposes of saving energy, reducing cost, simple operation and uniform blackening film. The room temperature blackening agent regulator effectively solves the above problems and achieves the required purpose.

Scope of application:

It is widely used for blackening at room temperature of various alloy steel、 cast iron products、machinery、hardware tools、standard parts、optical instruments and other metal products.

Characteristic:

Without heating, it can save more than 90% energy than the traditional high-temperature alkaline blackening process; Compared with similar products, the comprehensive cost can be reduced by about 30%;

Short blackening time, ready to use, simple operation, no environmental pollution, no need for exhaust facilities, so as to improve working conditions and work efficiency;

Blackening regulator can effectively increase the service life of blackening agent and improve its performance;

Appearance: blue transparent liquid without odor, volatile gas and corrosivity;

Stability: long term storage without deterioration.

Safety: non combustible, non explosive, safe transportation and storage.

The blackening film is dense and uniform, with deep blackness, no decolorization, and the film thickness is 10μm.

Strong adhesion and wear resistance are better than similar products.

Corrosion resistance:

① drip the mixed solution of 41g / L copper sulfate, 35g / L sodium chloride and 13ml 0.1mol/L hydrochloric acid at 15°C~20°C with analytical pure reagent and distilled water, and the discoloration time is more than 3 minutes;

3% chemically pure copper sulfate is used for dropping at 15 ° C ~ 20 ° C, and the discoloration time is more than 5 minutes;

② Drip 5% sulfuric acid solution to expose the substrate for more than 6 minutes;

Soak in 3% sodium chloride solution for more than 80 minutes.

5. Rust prevention treatment of steel surface:

Antirust treatment of iron and steel is usually divided into three methods and requirements: inter process antirust, processability antirust and final antirust.

The rust prevention treatment between processes generally adopts water-based rust prevention, dehydration rust prevention and other rust prevention methods, with short rust prevention time which can meet the rust prevention requirements between processes.

The processability antirust includes passivation antirust, phosphating antirust, dehydrated antirust oil etc., which are different due to different process requirements.

The final antirust treatment is mainly oily antirust. Because the antirust grease is not volatile, it has a long antirust time.

With the rapid development of industrial technology, rust prevention has gradually become the subject of concern. There are a series of products such as phosphating products, passivation products, blackening products, water-based rust inhibitors, dehydrated rust preventive oil, dural rust inhibitor and cutting rust preventive fluid.

Scope of application:

It is suitable for dehydration rust prevention, inter process rust prevention, process rust prevention and long-term sealing rust prevention of various metals or equipment after machining, grinding, heat treatment, electrolytic machining, blackening and bluing treatment and water-based cleaning.

Cleaning agent products

Cleaning agent series mainly includes powerful general cleaning agent, dairy equipment cleaning agent and bottle cleaning agent

Powerful general cleaning agent: with strong decontamination and oil removal ability, it has a significant cleaning effect on metal products and old scale and heavy scale on hard surfaces. It is an ideal product for cleaning in hotels, baths and public places.

Dairy equipment cleaning agent: including alkali cleaning agent, disinfection cleaning agent and acid cleaning agent, which has strong degreasing and decontamination cleaning effect, advanced technology, unique formula and low cost. CIP (on-site cleaning) method is adopted for cleaning. It is directly connected with the supply line equipment such as cleaning agent, steam and high-temperature water on the production line, which can achieve the effect of rapid cleaning and sterilization.

Bottle cleaner: Including industrial bottle washing agent, wine bottle cleaning agent, milk bottle cleaning agent and wine bottle sterilization cleaning agent. This kind of product has good hard water resistance, strong dirt dispersion, high brightness of washing bottle, no blocking of nozzle and pipeline of bottle washing machine, strong decontamination of bottle stopper and bottleneck rust, no corrosion of equipment and good sterilization effect.

Degreasing series products

Oil removal series products mainly include normal temperature type, medium temperature type and additives. Normal temperature deoiling agent: mainly including normal temperature deoiling agent, water-based deoiling agent, deoiling additive, wool washing agent, water emulsion leather degreasing agent and other products. This kind of product has unique formula, rapid degreasing and decontamination, and remarkable effect. It has no corrosion to the hard surface and metal materials, and the cleaned workpiece surface can still maintain the original luster. It is the preferred product for oil and scale removal of metal products, mechanical equipment, oil pipelines, boilers and hard surfaces and pretreatment of metal coating.

Medium temperature oil remover: this kind of product has low cost and good oil removal effect. It is the first choice for oil removal on the surface of steel, ferrous metal, aluminum and aluminum alloy.

Additive: it is a neutral product and can be added to acid and alkali cleaning agents to improve the cleaning effect. Adding it to the pickling and derusting solution can make the pickling solution achieve oil and derusting at one time; When added to iron series phosphating solution, the degreasing phosphating can be completed at one time; When added to alkaline degreasing agent, the degreasing effect can be significantly improved. It can also be used as neutral special degreasing cleaning agent.

Derusting products

Derusting products include derusting agents, derusting additives and pickling fog inhibitors. This kind of rust remover has high rust removal quality and good fog suppression effect. It is an indispensable product for metal pretreatment and metal equipment cleaning. Rust removal additive is composed of a variety of surfactants and special corrosion inhibitors. It has a good effect of inhibiting acid mist, preventing over corrosion and hydrogen embrittlement. It can keep metal materials free of corrosion and original metal luster, and significantly improve the service life of pickling rust removal solution. Hydrochloric acid added with additives can improve the rust removal speed and achieve the treatment effect of various ferrous metal oxide scale and rust.

Acid coating fog inhibitors include hydrochloric acid, sulfuric acid and mixed acid, which can inhibit the volatilization of various acid fog and make the volatilization of acid fog less than the allowable value specified by the state.

Rust prevention and passivation products

Antirust and passivation products mainly include antirust agent, dural antirust agent, dehydrated antirust oil, water-based antirust agent, passivation antirust agent, series passivator, blackening agent, blackening passivator, etc. they can be widely used in metal processing and manufacturing industry, metal product protection, metal post cleaning protection etc. with remarkable protection effect.

Phosphating series products

Phosphating series products mainly include normal temperature phosphating and high, medium and low temperature phosphating.

Normal temperature phosphating and low temperature phosphating include zinc calcium phosphating and iron phosphating, especially the normal temperature zinc calcium phosphating products. Under normal temperature, this kind of product has the advantages of fast film-forming speed, uniform and dense phosphating film, simple operation and low cost. It is an ideal agent for metal coating pretreatment.

Medium and high temperature phosphating is suitable for cold extrusion tensile phosphating, wear-resistant phosphating etc. It is widely used in infiltration phosphating and spray phosphating production lines.

Phosphating film is mainly used as the bottom layer of coating, lubricating layer during metal cold working, metal surface protective layer, insulation treatment of motor silicon steel sheet, anti sticking treatment of die casting die etc.

Phosphating solution and lubricant products are special phosphating and lubrication products for cold backlog and cold drawing industries. The phosphating solution and lubricant have the advantages of convenient operation, simple adjustment, medium temperature use, small dosage, large treatment area and low cost. The formed phosphating film and adsorbed lubricating film are dense and uniform, with good adhesion and strong corrosion resistance. Moreover, one lubrication process can replace the traditional saponification and boration processes to solve the problems of low production efficiency For the problems of slow drawing speed and short service life of abrasive tools, the amount of adsorption can be controlled at will.