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Author: Zhang Zuo-hua, Organization: Saihua Cloud. Surface treatment for anti-corrosion purposes can be divided into surface treatment for metal substrates and surface treatment for non-metallic substrates. Surface pre-treatment for metals includes pre-treatment of the surfaces of ferrous metals (such as steel) and non-ferrous metals (such as zinc and aluminum) ； The surface preparation for non-metallic surfaces includes concrete (such as cement concrete and resin concrete), as well as surfaces made of ceramics, granite, corrosion-resistant brick panels, plastics, glass, rubber, and fiberglass. The most common and largest-scale applications in anti-corrosion treatment are surface treatment of steel and surface treatment of cement concrete. Surface treatment at the base layer is the first and most crucial step in anti-corrosion construction; it directly affects the quality and service life of the anti-corrosion coating. To control the quality of surface treatment at the basic level and ensure that corrosion-resistant coatings maintain their effectiveness over the longest possible period, **relevant authorities have established mandatory standards, such as the GB8923 regulations for steel surface treatment** ； However, to date, there is no separate standard for the surface treatment of cement concrete; at most, there are only some design requirements. Having witnessed numerous failure cases of anti-corrosion coatings for cement concrete, such as quality issues involving bubbles, pinholes, and even complete delamination in resin, paint, fiberglass-reinforced plastic, and polyurea coatings, the author found that these problems are all directly related to the quality of surface treatment of the cement concrete. Therefore, it is necessary to discuss in writing the quality requirements and construction techniques for the surface treatment of cement concrete, as a supplement in the absence of specific regulatory standards. This is aimed at preventing the corrosion protection layer of cement concrete from failing due to improper surface treatment, and thus avoiding significant economic losses. A good bond between the cement concrete base layer and the anti-corrosion layer depends on the moisture content, surface treatment, and cleanliness. Many standards specify that the moisture content should be below 6%, with a maximum of 8%. Standards such as GB/T50590-2010 \"Technical Specifications for Anti-corrosion Engineering of Vinyl Ester Resins\", GB50224-2010 \"Code for Acceptance of Construction Quality of Building Anti-corrosion Engineering\", JGJ/T175-2018 \"Technical Standards for Self-leveling Floor Engineering\", GJG/T200-2010 \"Technical Regulations for Sprayed Polyurea Waterproofing Engineering\", and CECS328:2012 \"Technical Regulations for Monolithic Floor Engineering\" all stipulate that the moisture content in concrete should be around 6%, with a maximum of 8%. In anti-corrosion construction, the surface treatment of cement concrete and its cleanliness must ensure that there is no oil, no floating dust, no impurities, and no contaminants at all; the concrete should exhibit its natural color, natural pores, and a solid structure, with an appropriate level of roughness and cleanliness (as determined by visual inspection and touch). In fact, the absence of any pollutants is sufficient to meet the cleanliness requirements; the presence of these pollutants in cement concrete is the reason why cement concrete and coating materials cannot bond completely, and they must be removed thoroughly. Pollutants on the surface of cement concrete originate from the following sources: 1. Cement concrete curing fluids. Some of these curing fluids are compatible with the materials used for applying anti-corrosion coatings, while others are not, and in some cases chemical reactions even occur. Therefore, it must be completely removed. 2 Cement concrete slurry: Slurry is a weak layer that forms when aggregates settle and separate during concrete pouring; its thickness is roughly 1.6–3.2 mm. It is usually due to an improper water-cement ratio, or the concrete built at low temperatures being exposed to the air for an extended period, coupled with excessive troweling and polishing that brings cement paste to the surface of the concrete. Therefore, it must be thoroughly cleaned. 3 Cement concrete form release agents: When pouring concrete, in order to facilitate and speed up demolding, anti-adhesive liquid materials such as machine oil, diesel, or mixed oils are used, which remain on the surface of the cement concrete after demolding. Therefore, it must be completely removed. 4 Pollutants such as oils, greases, brake fluid, liquid paraffin, asphalt, and resins not only remain on the surface of concrete but also penetrate into its interior, and can even migrate into the anti-corrosion layer. Even if it’s difficult to handle, it must be thoroughly cleaned. 5 In cement concrete and salt-spray concrete, the salt precipitates migrate to the surface of the cement concrete along with water; once the water dries up, the crystal precipitates remain on the surface of the concrete. Therefore, it must be thoroughly cleaned. 6 Dust on the surface of cement concrete, whether it is dust caused by the surrounding environment or dust generated by mechanical grinding, must be removed using a vacuum cleaner or clean compressed air. 7 Contamination by other chemicals: Chemical raw materials or finished products from chemical plants, pharmaceutical factories, and pesticide manufacturers leak into the concrete, or they end up on its surface for various reasons. Therefore, it must be completely cleaned. Regardless of the type of material or the reason behind the contamination entering the interior or surface of the cement concrete, it must be thoroughly cleaned to ensure that the underlying surface meets the requirements necessary for applying the anti-corrosion coating. Only by ensuring the quality of surface treatment can the best adhesion between the anti-corrosion layer and the cement concrete base be achieved, thereby enabling the anti-corrosion layer to function optimally and have a long service life. There are many methods for surface treatment of cement concrete, with representative ones including: chemical cleaning, solvent cleaning, steam cleaning, flame cleaning, shot blasting, sandblasting, grinding, cleaning with vacuum and compressed air, high-pressure water cleaning, acid washing, and so on. For chemical cleaning, trisodium phosphate that can be dissolved in hot water or detergents can be used to clean the cement concrete, followed by rinsing with clean water; this method is applied to cement concrete contaminated by oil stains. Solvent cleaning involves using low-boiling-point solvents to scrub the surface of cement concrete, thereby removing contaminants as they are carried away by the solvent. This method is mainly used for cement concrete surfaces contaminated with oil, and safety must be taken into consideration during the cleaning process. Steam cleaning is an effective method for removing pollutants from cement concrete; it utilizes the high temperature and impact force of steam to act directly on the concrete surface, softening the pollutants so that they can be removed ； However, it has little effect on internal impurities and is mainly used to remove most pollutants from the surface of cement concrete. Flame cleaning involves using a flame gun to directly heat the surface of cement concrete, thereby removing contaminants through combustion and high temperatures. It is important to control the intensity of the heat applied to avoid damaging the strength of the concrete. This method is mainly used for cement concrete surfaces contaminated by oils such as grease, engine oil, hydraulic oil, and wax. Safety must be considered when using this technique. Shot blasting, sandblasting, and mechanical grinding are all methods that use abrasives to impact or rub against the surface of cement concrete in order to remove contaminants; however, these methods cannot deal with contaminants that have penetrated deep into the cement concrete ； However, it can create roughness and enhance the adhesion of the anti-corrosion coating; it is mainly used to remove cement slurry and other surface contaminants, and is a common surface treatment method for cement concrete. Cleaning with a vacuum and compressed air is a method used to deal with dust on the surface of cement concrete as well as liquid contaminants inside it. The vacuum can remove dust and absorb any liquid contaminants present inside, while compressed air is used to blow away surface dust and other pollutants. However, this cleaning method may cause environmental pollution, so it is recommended to use it in open areas. High-pressure water cleaning makes use of high-pressure water washers with a pressure of 12–16 MPa to remove the slurry, dust, and contaminants on the surface of cement concrete; it can also eliminate some contaminants inside the concrete. For pickling and cleaning, a 10% HCl solution is typically used to spray the surface of the cement concrete, thereby roughening it; this process is repeated until the surface roughness resembles that of medium-grit sandpaper. Afterwards, high-pressure water is used to remove any contaminants, and the pH level after washing should be neutral ； However, this method is applied in the absence of any coverage by oils, coatings, putties, asphalt, resins, or other organic pollutants, and it is rarely used in actual construction; it is only employed as a last resort when no other methods are available for treating the surface of cement concrete. Based on the author’s many years of experience in construction, surface treatment of cement concrete does not involve the use of a single method ； It is a combination of various treatment methods. Based on a large number of cases of concrete surface treatment, it is simpler to treat the surface of newly poured concrete than that of existing concrete ； When the moisture content of the newly poured concrete is below 6% and the surface is free of contaminants, methods such as sandblasting, shot blasting, or mechanical grinding can be used to remove the excess paste and impurities from the concrete surface, thereby giving it a certain level of roughness. If the surface is contaminated with oil, cleaning agents, solvents, or flame baking can be used to remove the oil. After it dries, sandblasting, shot blasting, or grinding can be carried out, and finally dust removal is done using a vacuum cleaner. If it is a non-oil contaminant, an appropriate process from the aforementioned cleaning methods can be selected for cleanup. The non-immersion treatment method for existing cement concrete is the same as that for newly constructed cement concrete ； For submerged cement concrete (such as sewage tanks), it is necessary to use the appropriate method from those listed above for cleaning; thereafter, it should be rinsed multiple times with high-pressure water. The pH value should be checked to ensure it is neutral, followed by drying with hot air. Sandblasting, shot blasting, or mechanical grinding may be used to create a certain level of roughness, and finally, dust and debris should be removed using a vacuum cleaner. To provide the anti-corrosion coating with a better bonding surface and to avoid defects such as bubbles, pinholes, and delamination, the treated substrate surface must be filled with putty to cover cracks, gaps, holes, and depressions, after which putty is applied evenly across the entire surface to achieve a smooth finish. In short, the surface treatment of cement concrete is not a simple grinding process; it has its own characteristics and quality requirements. By controlling the quality of the surface treatment process, it is possible to **significantly improve the corrosion resistance and service life of the cement concrete protective layer ； Moreover, it is of great significance for the long-term corrosion prevention of cement concrete. The author suggests that the surface treatment of cement concrete should be treated in the same way as the quality requirements for steel surface treatment specified in GB8923. Although no mandatory standards for the surface treatment of concrete have been established yet ； However, practical experience tells us that it is necessary to meet the surface requirements of the anti-corrosion coating for the base material, as well as to take the necessary measures to avoid defects. With the improvement in people’s living standards and the acceleration of industrialization, a large number of cement concrete floors, chimneys, waste tanks, and sewage tanks have now been equipped with anti-corrosion painting, thereby enhancing their aesthetic value as well as their resistance to corrosion. This places higher demands on the quality of surface treatment for cement concrete. Therefore, the author strongly calls on **the relevant authorities to establish independent standards for the surface treatment of cement concrete as soon as possible, in order to meet the rapidly growing demands for corrosion prevention and beautification