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Brief talk metal surface cleaning technology

Metal parts are widely used in our social life and are the most important industrial raw materials. However, the surface is easily contaminated and corroded by the medium. In order to reduce material loss, extend the service life of materials, and maintain good working conditions, we need to clean and rust proof the surface,

The main sources of pollutants are:

Atmosphere: Dust and other pollutants in the atmosphere deposit on solid surfaces to produce dirt.

Cooling medium: For example, cooling water contains inorganic salts such as Ca (Mg) (HCO3) 2, which decompose into scale when heated and deposit on the inner surface of the cooling water system to form inorganic salt scale.

Production raw materials and products: When production equipment comes into contact with pipelines and production materials, some reaction products or intermediates may deposit on the inner surface of the equipment and thicken over time.

Mechanical oil: Lubricating oil, rust proof oil, hydraulic oil, and their additives used in machinery may be introduced into the production system, contaminating equipment or material surfaces and forming difficult to remove oil stains.

Microorganisms: Microorganisms that grow in water and soil generate microbial sludge on the surfaces of equipment and pipelines.

Surface processing products: The artificial coating, plating, lining, and lining layers on the surface of materials and equipment need to be cleaned before processing after being damaged, and the old surface protective layer becomes the dirt that needs to be cleaned. 

Corrosion products: Engineering materials (mainly steel and other materials) corrode under the action of corrosive substances in environmental media and production raw materials, producing rust products and forming rust scales. The purpose of industrial cleaning is to improve the appearance of equipment, maintain normal production, increase productivity, reduce energy consumption, and minimize production accidents.

Common knowledge of metal pretreatment

Pre treatment before phosphating generally requires that the surface of the workpiece should be a clean metal surface (except for 2-in-1, 3-in-1, and 4-in-1). Before phosphating, the workpiece must undergo pre-treatment such as degreasing, rust removal, rust removal, and surface adjustment. Especially for phosphating before painting, surface adjustment is required to give the metal surface a certain degree of "activity" in order to obtain a uniform, fine, and dense phosphating film, which can improve the adhesion and corrosion resistance of the paint film. Therefore, pre-treatment before phosphating is the foundation for obtaining high-quality phosphating films.

The purpose of degreasing is to remove grease and oil stains from the surface of the workpiece. The methods of rust removal, acid pickling, rust removal, and oxide scale removal have been widely used in the industrial field. The mechanical peeling effect of acid on the dissolution and corrosion of oxides to produce hydrogen gas is used to achieve the purpose of rust removal and scale removal. The purpose of surface adjustment is to promote the formation of a finely grained and dense phosphating film, as well as to improve the phosphating speed. Pre treatment process for phosphating: degreasing → water washing → acid washing → water washing → neutralization → surface adjustment → phosphating → water washing, oil and rust removal "two in one" → water washing → neutralization → surface adjustment → phosphating, oil and grease removal → water washing → surface adjustment → phosphating → water washing

Rust proof phosphating process

The early application of phosphating technology was rust prevention. Steel parts were treated with phosphating to form a layer of phosphating film, which played a role in rust prevention. The general process of rust prevention and phosphating includes oil and rust removal, water cleaning, surface adjustment and activation, phosphating, water cleaning, chromate treatment, drying, coating with grease or dyeing, wear-resistant and friction reducing lubrication phosphating. For workpieces such as engine piston rings, gears, and refrigeration compressors, they not only bear one load, but also have motion friction, requiring the workpiece to be able to reduce and resist friction. Manganese based phosphating film has high hardness and thermal stability, can withstand wear, and has good anti friction and lubrication effects. Therefore, it is widely used in components such as piston rings, bearing supports, compressors, etc. In the cold processing industry, processes such as takeover, drawing, extrusion, and deep drawing extension require phosphating films to provide anti friction and lubrication properties. Generally, a phosphating film layer with rough crystallization and high content of free acid, insufficient nitrate ions, residual acid on the surface, high content of ferrous ions, excessive corrosion of the workpiece surface, insufficient content of accelerators to reduce free acid, supplementing the original solution, strengthening neutralization and water washing, controlling acid washing concentration and time, using hydrogen peroxide to eliminate excess ferrous ions, and adding accelerators to remove dust from the phosphating film

There is a lot of sedimentation in the tank solution, the acid ratio is high, and the temperature is high. Remove the residue in the tank solution and filter it regularly. Add phosphating agent to adjust the acid ratio to the working range and reduce the temperature

The phosphating film is too thin, and the surface of the workpiece has a hardened layer. The temperature of the tank solution is low, the phosphating time is short, and the surface adjustment effect is poor or ineffective. Strong acid rust removal is used to remove the hardened layer, and the tank solution temperature is increased to extend the phosphating time. After replacing or supplementing the surface adjustment phosphating, the surface rusts or becomes discolored. The workpiece has already rusted before phosphating. The technical indicators of the tank solution are incorrect, the temperature is too low, the water washing tank solution is contaminated, the oil removal is not clean, and the surface adjustment effect is poor or ineffective. Before phosphating, sandpaper is used to polish or re remove rust, check the free acidity, total acidity, accelerator and tank solution temperature, increase the water washing overflow flow rate, strengthen oil removal or replace the degreaser, replace or supplement the surface adjustment phosphating film formation speed. The total acidity or temperature of the tank Phosphating agent, increase the temperature of the phosphating tank solution to the working range, Adding accelerators to the phosphating tank results in excessive precipitation and low free acidity. If the main salt content in the phosphating tank solution is too high, increase the free acidity appropriately, dilute the phosphating tank solution with water, and adjust the corresponding indicators.

Pre treatment before phosphating

In general, phosphating treatment requires that the surface of the workpiece should be a clean metal surface (except for 2-in-1, 3-in-1, and 4-in-1). The workpiece must undergo pre-treatment such as degreasing, rust removal, oxide coating, and surface adjustment before phosphating. Especially for phosphating before painting, surface adjustment is required to give the metal surface a certain degree of "activity" in order to obtain a uniform, fine, and dense phosphating film, which can improve the adhesion and corrosion resistance of the paint film. Therefore, pre-treatment before phosphating is the foundation for obtaining high-quality phosphating films.

1.Remove oil and grease

The purpose of degreasing is to remove grease and oil stains from the surface of the workpiece. Including two types: mechanical methods and chemical methods. Mechanical methods mainly include manual brushing, sandblasting, shot blasting, flame burning, etc.

Chemical methods mainly include solvent cleaning, acidic cleaning agent cleaning, strong alkaline solution cleaning, and low alkaline cleaning agent cleaning. The following introduces the chemical degreasing process.

1.1 Solvent cleaning

The solvent method for removing oil and grease is generally used by non flammable halogenated hydrocarbon vapor method or emulsification method. The most common method is to use trichloroethylene, trichloroethylene, and perfluoroethylene steam to remove grease. Steam degreasing has fast speed, high efficiency, thorough degreasing, and excellent removal effect on various oils and fats. Adding a certain amount of emulsion to chlorinated hydrocarbons has good soaking and spraying effects. Due to the toxicity of chlorinated halogens and the high vaporization temperature, as well as the emergence of new water-based low alkaline cleaning agents, solvent vapor and lotion degreasing methods are rarely used now.

1.2 Acidic cleaning agent cleaning

Acidic cleaning agents are a widely used method for removing grease. It utilizes the principles of emulsification, wetting, and permeation of surfactants, and utilizes the mechanical stripping effect of hydrogen gas generated by acid corrosion of metals to achieve the purpose of removing grease. Acidic cleaning agents can be used at low and medium temperatures. Low temperature can generally only remove liquid oil, while medium temperature can remove oil and grease, and is generally only suitable for soaking treatment. Acidic cleaning agents are mainly composed of three parts: surfactants (such as OP non-ionic surfactants and anionic sodium sulfonate), ordinary inorganic acids, and corrosion inhibitors. Due to its dual functions of rust removal and grease removal, it is commonly referred to as a "two in one" treatment solution. Hydrochloric acid and sulfuric acid based cleaning agents are widely used, with low cost and high efficiency. However, the residual Cl - and SO42- from acid washing pose significant post corrosion hazards to the workpiece. Phosphoric acid groups do not pose a risk of residual corrosive substances, but phosphoric acid has a higher cost and lower cleaning efficiency. For zinc parts, aluminum parts are generally not cleaned with acidic cleaning agents, especially as zinc parts corrode rapidly in acid.

1. Oil removal treatment of steel surface:

We have learned that 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 oil removal methods have different oil removal characteristics. Solvent degreasing is the process of using the structural similarity between organic solvents and oil stains to dissolve them in organic solvents, achieving the goal of degreasing; Electrochemical oil removal generally uses dilute alkaline solution as the electrolyte and the workpiece as the electrode for electrolytic treatment. The gas released on the electrode surface during electrolysis is used to forcibly remove the oil stains from the surface of the workpiece; Chemical degreasing is the process of removing oil through the saponification reaction between alkali and oil stains; Surfactant oil removal is achieved through its emulsification, solubilization, wetting, dispersion, and other functions. Mechanical and manual oil removal are self-evident.

In modern oil removal technology, the synergistic effect of several substances is often used to achieve the best oil removal effect. The room temperature degreasing agent produced by our company is an advanced, fast, and efficient degreasing cleaning agent at room temperature. It is a mixed degreasing cleaning agent of sodium salt, surfactant, and organic solvent.

Scope of application: Suitable for degreasing and cleaning of steel products before electroplating, blackening, phosphating, and during metal processing.

Product features:

It can effectively clean various oil stains on the surface of steel at room temperature;

Excellent performance, good stability, short oil removal time, and long product lifespan&# 160;

Has strong abilities in decontamination, dispersion, emulsification, and solubilization;

Easy to operate and energy-saving.

It is the best choice for removing oil at room temperature.

2. Rust removal treatment of steel surface:

During the processing of steel products, the oxide scale and rust on their surface must be chemically cleaned to expose the steel substrate, effectively improving the treatment effects of electroplating, phosphating, oxidation (black hair blue), stretching, rolling, rolling, rust prevention, etc.

The most commonly used method for chemical rust removal is hydrochloric acid rust removal, which is widely used because it has a fast rust removal speed and can be carried out at room temperature. However, in practical operation, hydrochloric acid rust removal suffers from "over corrosion" and "hydrogen embrittlement" phenomena, producing a large amount of acid mist, causing environmental pollution and social hazards. To overcome the above problems, our company has developed a rust removal additive that combines corrosion inhibition and mist suppression, improving and solving the practical problem of hydrochloric acid rust removal.

Scope of application: Suitable for rust removal treatment of steel products before electroplating, blackening, phosphating, and during metal processing.

Product features: This rust removal additive is mixed with hydrochloric acid and has the following characteristics: fast rust removal speed and good rust removal effect at room temperature;

It has the functions of infiltration, dissolution, dispersion, and removal of oxide scale and rust;

Good quality. The rust removal quality meets or exceeds the Swedish rust removal standards; Sa Level 3, West German Be Level;

Good corrosion and fog inhibition effect. Due to the synergistic effect of various additives in the solvent, steel will not experience excessive corrosion and hydrogen embrittlement during the rust removal process. The acid mist standard is lower than the concentration specified by the state, which is beneficial for the post-treatment of rust removal;

Low cost. The cost of rust removal is only about 0.15 yuan/square meter. After repeated use, one ton of solution can treat about 5000-7000 square meters of workpieces with first level rust removal, which is 1/10 of sandblasting rust removal and 1/2 of pickling rust removal;

Widely applicable. Suitable for various sizes and complex components of steel products;

Improve working environment and conditions, reduce labor intensity, do not harm the physical health of operators, and do not consume energy.

3. Phosphating treatment of steel surface:

Phosphating Overview: Phosphating is a commonly used pre-treatment technique, which should theoretically belong to chemical conversion coating treatment. The main application in engineering is surface phosphating of steel parts, but phosphating can also be applied to non-ferrous metals such as aluminum and zinc parts.

Phosphating principle: The process of immersing workpieces (steel or aluminum, zinc parts) in a phosphating solution (a solution mainly composed of certain acid phosphates) and depositing a water-insoluble crystalline phosphate conversion film on the surface is called phosphating. The method of chemically treating metals by placing them in a phosphate solution containing manganese, iron, and zinc to form a water-insoluble phosphate protective film on the metal surface is called metal phosphate treatment. The phosphating film layer has a microporous structure and is firmly bonded to the substrate. It has good adsorption, lubrication, corrosion resistance, non adhesion to molten metals (Sn, Al, Zn), and high electrical insulation properties.

Phosphating classification: Classified by processing temperature: high temperature type (75-100 ℃, high energy consumption, high deposition of phosphides, forming a phosphating film thickness of 10-30g/㎡), medium temperature type (50-75 ℃, processing time 5-15 minutes, phosphating film thickness of 1-8g/㎡), low temperature type (30-50 ℃), and room temperature type (10-30 ℃, energy-saving, easy to use, adding accelerators in addition to oxidants, low energy consumption, but complex solution preparation, film thickness of 0.2-7g/㎡).

According to the composition of the phosphating solution, it can be divided into zinc based phosphating, zinc calcium based phosphating, zinc manganese based phosphating, iron based phosphating, manganese based phosphating, and composite phosphating.

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

According to the quality of the phosphating film, it can be divided into heavyweight (film weight of 7.5g/㎡ or more), sub heavyweight (film weight of 4.6-7.5g/㎡), lightweight (film weight of 1.1-4.5g/㎡), and sub lightweight (film weight of 0.2-1g/㎡). Divided by construction methods: immersion phosphating, spray phosphating, and brush phosphating.

Phosphating effect and use:

The function of phosphating before painting: to enhance the adhesion between the coating layer (such as paint coating) and the workpiece; Improve the corrosion resistance of the surface coating of the workpiece after painting; Improve decorative quality.

The function of non coating phosphating is to improve the wear resistance of the workpiece and provide lubrication during the machining process; After appropriate post-processing, the wear resistance of the workpiece can be improved.

Phosphating application: Phosphating film is mainly used as the bottom layer of coatings, lubricating layer during metal cold processing, metal surface protective layer, as well as insulation treatment for motor silicon steel sheets, anti sticking treatment for die-casting molds, etc. Widely used in industrial production such as automobiles, ships, aerospace, machinery manufacturing, and home appliances.

The necessity of phosphating: The pre-treatment process for steel surface coating includes degreasing (oil removal), rust removal, surface adjustment, and phosphating. However, due to the different surface conditions of the workpiece, the production process also varies. Some processes do not have degreasing or rust removal procedures, while others do not have surface adjustment procedures. However, phosphating is absolutely indispensable.

During the painting process, if the grease, oxide scale, and rust layer are not removed, and phosphating treatment is not carried out, direct painting and electrostatic spraying will cause the coating on the steel surface to peel off, losing the meaning of painting&# 160;

At present, the metal processing industry, sheet metal processing industry, petroleum industry, as well as manufacturing industries such as automobiles, bicycles, high and low voltage switchgear, anti-theft doors, railways, etc. commonly use medium and high temperature phosphating, which has problems such as inconvenient operation, high energy and material consumption, frequent adjustment, uneven film formation, and high cost. To solve the above problems, room temperature phosphating has become an inevitable and research topic in the international phosphating industry. Room temperature phosphating can not only effectively reduce energy consumption, but also solve problems such as inconvenient operation, high material consumption, frequent adjustment, uneven film formation, and high cost.

Based on the above reasons, our company's research and production of room temperature zinc manganese phosphating solution, room temperature iron phosphating solution (powder) and other products effectively meet the process requirements of room temperature phosphating. This type of phosphating product has stable performance, easy operation, simple adjustment, room temperature application, energy saving, low dosage, large processing area, low cost, and forms a dense and uniform phosphating film with good adhesion and strong corrosion resistance.

4. Blackening treatment of steel surface

The traditional blackening method is alkaline oxidation blackening. Alkaline oxidation blackening is usually achieved by using high temperature and nitrite as oxidants to heat and oxidize steel parts in an extremely concentrated alkaline oxidation solution, forming a protective blue to black Fe3O4 oxide film on the surface of the parts. This high-temperature oxidant causes uneven heating and high temperature during blackening of the workpiece, resulting in rapid changes in the solution content and often causing uneven blackening of the film. So people are eager to seek room temperature blackening technology to achieve the goals of energy saving, cost reduction, easy operation, and uniform blackening film. The room temperature blackening agent adjustment agent developed and produced by our company effectively solves the above problems and achieves the required goals.

Scope of application:

This product is widely used for room temperature blackening treatment of various alloy steel, cast iron products, machinery, hardware tools, standard parts, optical instruments and other metal products.

Product features:

No need for heating, saving over 90% energy compared to traditional high-temperature alkaline blackening process;

Compared with similar domestic products, the overall cost can be reduced by about 30%;

Short blackening time, on-demand use, easy operation, no pollution to the environment, no need for exhaust facilities, achieving the goal of improving working conditions and increasing work efficiency;

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

Appearance: odorless, non-volatile, non corrosive blue transparent liquid;

Stability: Long term storage without deterioration.

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

The black film is dense and uniform, with a deep blackness, no discoloration, and a film thickness greater than 10 μ m.

Strong adhesion and superior wear resistance compared to similar products.

Corrosion resistance:

① Using analytical pure reagents and distilled water, a mixed solution of 41g/l copper sulfate, 35g/l sodium chloride, and 13ml 0.1mol/l hydrochloric acid is dripped at 15 ℃ -20 ℃, with a color change time of more than 3 minutes;

② Drip 3% chemically pure copper sulfate at 15 ℃ -20 ℃, with a color change time of more than 5 minutes;

③ Drip 5% sulfuric acid solution and expose the substrate for more than 6 minutes;

④ Soak in a 3% sodium chloride solution for more than 80 minutes to remove rust.

5. Rust prevention treatment on steel surface:

The rust prevention treatment of steel is usually divided into three methods and requirements: inter process rust prevention, process rust prevention, and final rust prevention.

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

Process based rust prevention treatments include passivation rust prevention, phosphating rust prevention, dehydration rust prevention oil, etc., which vary depending on the process requirements.

The final rust prevention treatment is mainly oil-based rust prevention. Because anti rust grease is not easily volatile, its anti rust time is longer.

The development of rust prevention technology for steel in China is still in its early stages, and people lack awareness or understanding of rust prevention methods. The rust prevention processes and products used are still some traditional concepts. With the rapid development of industrial technology in our country, rust prevention has gradually become a topic of concern for people. Therefore, our company has developed, produced, and provided a series of rust prevention processes and products that well meet the needs of this industrial development. Its products include phosphating products, passivation products, blackening products, water-based rust inhibitors, dehydrated rust preventive oil, hard film rust inhibitors, and cutting rust inhibitors.

Scope of application:

Suitable for dehydration rust prevention, inter process rust prevention, process rust prevention, and long-term storage rust prevention of various metals or equipment after mechanical processing, grinding, heat treatment, electrochemical processing, hair orchid treatment, and water-based cleaning.

The phosphating series products mainly include two categories: room temperature phosphating and high, medium, and low temperature phosphating.

Room temperature phosphating and low-temperature phosphating include zinc manganese phosphating and iron phosphating, with FH-LH room temperature zinc manganese phosphating products being particularly representative. This type of product has a fast film-forming speed, uniform and dense phosphating film, easy operation, and low cost at room temperature, making it an ideal agent for metal coating pretreatment.

High temperature phosphating is suitable for cold extrusion stretching phosphating, wear-resistant phosphating, etc. The heating phosphating effect is good, the film formation is fast, and it is widely used in immersion phosphating and spray phosphating production lines

Phosphating film is mainly used as the bottom layer of coatings, lubricating layer during metal cold processing, metal surface protective layer, as well as insulation treatment for motor silicon steel sheets and anti sticking treatment for die-casting molds.

Cold extrusion phosphating, cold drawing phosphating, cold extrusion lubrication, and cold drawing lubrication products are currently mostly traditional single passivation, saponification, and boronization products in China, which have complex lubrication processes and unsatisfactory effects. Our company draws on advanced technologies from both domestic and international sources to develop FH-LH8 phosphating solution and FH-RR lubricant products, which are high-tech composite products that integrate multiple processes and technologies. They are specialized phosphating and lubrication products developed for the cold backlog and cold drawing industries. The phosphating solution and lubricant are easy to use, easy to adjust, used at medium temperatures, with small amounts, large processing areas, and low costs. 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 boronization processes, solving problems such as low production efficiency, slow drawing speed, and short service life of grinding tools. The amount of adsorption can also be freely controlled

The phosphating series products mainly include two categories: room temperature phosphating and medium high temperature phosphating

Room temperature phosphating

Including zinc manganese phosphating and iron phosphating, the FH-LHC1 room temperature zinc manganese phosphating product is particularly representative. This type of product has a fast film-forming speed, uniform and dense phosphating film, easy operation, and low cost at room temperature, making it an ideal agent for metal coating pretreatment.

Medium high temperature phosphating

Suitable for cold extrusion stretching phosphating, wear-resistant phosphating, etc. The heating phosphating effect is good, the film formation is fast, and it is widely used in immersion phosphating and spray phosphating production lines