1 Emerging marine engineering: offshore facilities, coastal and bay structures, offshore oil platforms;
2 Modern transportation: highway guardrails, bridges, boats, containers, trains and railway facilities, automobiles, airport facilities;
3 Energy industry: hydraulic equipment, water tanks, petroleum refining equipment, petroleum storage equipment (oil pipes, oil tanks), power transmission and transformation equipment, nuclear power, coal mines;
4 large-scale industrial enterprises: papermaking equipment, medical equipment, food and chemical equipment, metal containers inside and outside walls, pipes of chemical, steel, petrochemical plants, storage tanks, mining smelting, cement plant equipment, ground with corrosive media, wall cement components;
5 Municipal facilities: gas pipelines and their facilities (such as gas cabinets), natural gas pipelines, drinking water facilities, garbage disposal equipment, etc.
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The main difference between heavy-duty anti-corrosion coatings and conventional anti-corrosion coatings is that they are high in technical content and technically difficult. They involve many aspects of technological advancement and product development. They no longer rely too much on the knowledge and experience of coatings, but on electronics, Multidisciplinary knowledge and convergence of physics, ecology, machinery, instrumentation and management, synthesis of highly corrosion-resistant resins, application of high-efficiency dispersants and rheological additives, development of new corrosion-resistant and impervious pigments and fillers, and advanced construction tools Applications, construction and maintenance techniques, on-site inspection techniques, etc., need to be integrated into heavy-duty coatings and coatings. Therefore, the development level of heavy anti-corrosion coatings, how to achieve performance, has become a symbol of a country's scientific and technological level, and has become a symbol to measure the advanced technology of anti-corrosion coatings.
Surface treatment
Surface treatment includes degreasing, descaling, surface defects removal, adhesion enhancement and corrosion resistance of the coating, so surface treatment is the key to good coating results.
Degreasing
Removing the oil stain on the surface of the metal workpiece can enhance the adhesion of various coatings. The method of removing oil is as follows:
Solvent cleaning: Commonly used solvents are 200# solvent oil, X-6 or X-61 alkyd thinner, etc.
Lye cleaning
Emulsification and degreasing (ie surfactant cleaning): Commonly used emulsified oils are: A-20, OS-15/OP-10
Ultrasonic degreasing
2. Rust removal
Different steel parts have different derusting standards on the surface. It is classified according to the cleanliness of the steel surface after derusting. Different descaling methods reach different standards.
Corrosion differs in four levels:
The surface of the Class A steel completely covers the adhered scale and is almost free of rust.
The surface of the B-grade steel has begun to rust, and the scale begins to fall off in a sheet.
The oxide scale on the surface of Class C steel has been rusted or scraped, but slight rust is visible to the naked eye.
The scale on the surface of the D-grade steel has been rusted and peeled off, and a large number of rust spots can be seen in the naked eye.
According to SISO55900, the surface treatment of these rust grades is based on the following quality standards for wire brush rust removal and sand blasting:
St——Wire brush derusting standard St2, St3
Sa——Sand blasting standard Sa1, Sa2, Sa2.5, Sa3
Sandblasting and rusting - Sa
All thick rust layers that should be cut before blasting and rust removal, visible grease and dirt should also be removed. After blasting the rust, the surface should be clean and free of dust and debris.
Sa1 grade mild sandblasting and rust removal
The surface should be free of visible grease, dirt, loosely attached oxide scale, rust, paint coatings and impurities.
Sa2 level thorough sandblasting and rust removal
The surface should be free of visible grease, dirt, scale, rust, paint coatings and impurities, and the residue should be firmly attached.
Sa2.5 level very thorough sandblasting and rust removal
The surface should be free of visible grease, dirt, loosely attached oxide scale, rust, paint coatings and impurities. The traces of the residue show only a slight stain with a streak of streaks.
Sa3 grade sandblasting and rust removal to steel
The surface should be free of grease, scale, rust, paint coatings and magazines with a uniform metallic colour on the surface.
Wire brush rust removal - St
St2 thorough manual and power tool rust removal
The surface should be free of visible grease, dirt, loosely attached oxide scale, rust, paint coatings and magazines.
Sa3 very thorough manual and power tool rust removal
The common method is chemical descaling: usually also called pickling, which uses an acid solution to promote the morphological change of the rust layer on the surface of the part and dissolve it in the acid solution to achieve the purpose of derusting.
3. Common methods for removing old paint films are: mechanical removal, lye and emulsion wash removal, organic solvent removal, and removal with paint remover.
4. Phosphating treatment
The process of treating a metal product with an orthophosphoric acid solution of iron, manganese, zinc or cadmium to form an insoluble phosphate protective film on the surface of the metal product is called metal phosphating.
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