Analysis and application of metal surface coating on steel pipe protection

Anti-corrosion of paints generally requires pretreatment of the equipment surface, but surface pretreatment is labor-intensive and expensive, leaving hidden dangers if you are not careful, so some projects require paints to be rusty, wet, and with old paint film It can be installed even on the bottom surface; because some projects are very difficult to overhaul, it is required to extend the life of the anticorrosive material at one time; some projects require the coating itself to have functions such as heat, chemical resistance, biological corrosion, and oil resistance; some projects The coatings are required to be non-toxic and environmentally friendly; some projects require the coatings to be decorative; most projects require the coatings to be water-resistant, weather-resistant, moisture-resistant, fatigue-resistant, and mechanically strong, etc. Since the coating is composed of a base material, a pigment and a filler and a solvent, the base material is a film-forming substance and is the main component, and the pigment and filler have anti-rust pigments and flake fillers, and the solvent is used to dissolve the base material to facilitate film formation. Performance coatings have been continuously improved and developed under the above requirements.

In summary, longevity, reliability, labor saving, environmental protection, and economy are the general requirements for contemporary high-performance anti-corrosion coatings. The coating industry is developing toward powder, high solids, water-based, ultraviolet light curing, pollution-free, and resource-saving. Significant technological progress has the following aspects:

(1) Improve anti-corrosion performance: The study believes that the scale coating has a better isolation effect on metals and has an outstanding anti-seepage function. The high-solids coating makes the coating smooth and dense, anti-sagging, and has no pinholes, which greatly improves the corrosion resistance. There is also a fluorine-containing coating, which is resistant to various chemical substances and has a lifespan that is three times longer than ordinary coatings.

(2) Both cathodic protection functions: The water-based inorganic zinc-rich coating is a one-liquid-solid two-component coating, and the binder is a high molar ratio alkaline potassium silicate solution. Sex, so it has longer weather resistance and durability.

(3) Green paint: The aforementioned water-based inorganic zinc-rich paint is a zero-VOC environmentally friendly paint. Another environmentally friendly coating is alkyd modified resin coating, which can replace chlorinated rubber. Chlorinated rubber contains a large amount of chlorine, which makes the water permeability very low and has good water resistance. It is one of the main film-forming substances of anti-corrosion coatings. However, chlorinated rubber pollutes the atmosphere and now has excellent performance. Alternative products can completely overcome this shortcoming.

(4) New material development: development of weathering steel. Carbon steel and ordinary low alloy steel have to rust in the atmosphere, and it is very expensive to use various methods to prevent rust.

The protection of coatings on metal surfaces is not seamless, and corrosion will always develop on weak links. The combination of high-quality paint and cathodic protection is a relatively complete protection scheme. There are two methods for cathodic protection of steel pipes: impressed current method and sacrificial anode method: impressed current method adopts adjustable DC current to the steel pipe to be protected, the positive pole of the power supply is connected to the auxiliary anode, and the negative pole of the power supply is connected to the steel pipe The surface area accumulates enough electrons to form a whole cathode to be protected; the sacrificial anode method uses a metal with a negative potential than steel as the anode and the steel pipe in series. Due to the electrolysis, the sacrificial anode is continuously corroded and the steel pipe is protected.

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