What are the differences in surface preparation methods for different types of substrates before spraying Teflon coating?

There are certain differences in the surface treatment methods of different types of substrates before spraying Teflon coating. The following are the treatment methods of common substrates and their differences:
Metal substrate
Steel substrate
Degreasing and degreasing: There are often pollutants such as oil and grease on the surface of steel. Organic solvents (such as gasoline, trichloroethylene, etc.) can be used for soaking and wiping or alkaline degreasing agents for chemical degreasing to remove oil and ensure the adhesion of the coating to the substrate.
Rust removal: Steel is easy to rust. For rusty steel substrates, rust removal is required. Acid pickling can be used to remove rust, such as soaking in acid solutions such as hydrochloric acid and sulfuric acid to remove rust; sandblasting can also be used to remove rust, using high-speed sprayed sand particles to impact the steel surface to remove rust and oxide scale, while forming a certain degree of roughness on the surface to enhance the adhesion of the coating.
Phosphating treatment: In order to further improve the adhesion and corrosion resistance of the coating, the steel substrate can be phosphated. The steel workpiece is immersed in a solution containing phosphate, and a layer of phosphate chemical conversion film is formed on its surface through chemical reaction, providing a good base for the Teflon coating.
Aluminum and aluminum alloy substrates
Degreasing and degreasing: Similar to steel substrates, organic solvents or alkaline degreasing agents can be used to remove oil stains on the surface of aluminum and aluminum alloys, but be careful to choose a mild degreasing agent to avoid corrosion on the aluminum surface.
Chemical conversion treatment: The commonly used surface treatment methods for aluminum and aluminum alloys are chemical oxidation or anodizing. Chemical oxidation uses chemical solutions to form an oxide film on the aluminum surface to improve corrosion resistance and coating adhesion; anodizing uses aluminum products as anodes in an electrolytic cell to form a thicker and harder oxide film on its surface through electrolysis, which can better improve the adhesion and wear resistance of the coating.
Grinding treatment: For some aluminum and aluminum alloy products with high surface roughness requirements, grinding treatment can be performed after chemical treatment, such as mechanical grinding or manual grinding, so that the surface roughness reaches an appropriate range, which is conducive to the uniform adhesion of the Teflon coating.
Plastic substrates
Surface cleaning: The plastic surface is usually smooth and may have residual impurities such as mold release agents and dust. First, wipe the plastic surface with organic solvents such as alcohol and acetone to remove oil and dust; for some release agents that are difficult to remove, special release agent cleaning agents can be used for treatment.
Roughening treatment: In order to improve the adhesion between the Teflon coating and the plastic substrate, the plastic surface needs to be roughened. Chemical corrosion methods can be used, such as using mixed acid solutions such as chromic acid and sulfuric acid to corrode the plastic surface to make its surface microstructure rough; physical methods such as sandpaper polishing and sandblasting can also be used, but attention should be paid to controlling the degree of treatment to avoid excessive roughening and causing the plastic surface performance to deteriorate.
Activation treatment: After roughening treatment, the active groups on the plastic surface increase, but in order to further improve the adhesion of the coating, activation treatment can also be performed. For example, plasma treatment technology is used to chemically react with the plastic surface through plasma, introduce some polar groups, increase surface energy, and enhance the bonding with the Teflon coating.
Ceramic substrate
Cleaning treatment: The ceramic surface is generally clean, but there may be some dust and impurities. Use deionized water or organic solvent to ultrasonically clean the ceramic surface to remove dust and tiny particles; for some ceramics with oil on the surface, use alkaline cleaning agent to clean, then rinse with deionized water and dry.
Surface modification: In order to improve the bonding performance between Teflon coating and ceramic substrate, the ceramic surface can be modified. One method is to use silane coupling agent to treat, apply silane coupling agent on the ceramic surface, and form a layer of organic silicon film on the ceramic surface through chemical reaction to improve the compatibility and adhesion between the ceramic surface and Teflon coating; another method is to deposit a layer of transition metal film, such as titanium, chromium, etc., on the ceramic surface through surface coating technology, such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), and then spray Teflon coating to improve the bonding strength of the coating.
Different types of substrates need different surface treatment methods before spraying Teflon coating due to their different material properties and surface states to ensure good adhesion between the coating and the substrate and uniformity of the coating, thereby improving the performance and service life of Teflon coating.