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Metal surface treatment during painting
For metal castings, our common surface treatment methods are mechanical grinding, chemical treatment, surface heat treatment, spray surface, surface treatment is to clean, clean, deburr, degrease, deoxidize the surface of the workpiece. The surface treatment of metal is also particularly important in the coating process, which is related to the quality and effect of the coating. Next, I will give you a detailed introduction to the metal surface treatment during the painting process.
1. The importance of pre-treatment of metal coating
For metal anti-corrosion coatings, there are many factors affecting the performance of the coating, such as coating composition, coating form, substrate surface pretreatment, coating structure, coating method, coating quality monitoring and coating post-treatment, etc. The reasons are divided into four categories: improper selection of coating system accounted for 20%; substrate surface treatment is not ideal 40%; coating thickness is not enough or unevenness accounted for 20%; coating management and process irrational accounted for 20%. This shows the importance of metal surface treatment.
2. Metal substrate pretreatment purpose
(1.) The bonding strength (adhesion) of the reinforced coating (paint film) to the metal surface of the object to be coated. The pretreatment methods include: mechanical roughening, chemical reaction film formation, chemical (physical) adsorption, preparation of transition layers, and combinations. Effect, etc.
(2.) Improve the protection (preservative) performance of the coating on the substrate, such as coating the steel after galvanizing;
(3.) Create good conditions for the flatness (fullness) of the coating, and improve the appearance and decoration of the coating, such as scraping putty.
3. Metal pre-treatment content
(1.) Structural processing
Sharp angles, spatters, welding slag, welding holes, etc., chamfering to reduce stress concentration.
(2.) Surface cleaning
Oxide (rolling), rust, soluble salts, oils and fats, insoluble solids, moisture (excluding water-based paints), etc.
(3.) Surface roughness
Improve the roughness and increase the mechanical bite of the coating and the substrate. If the roughness is too large, the convex portion may cause the partial coating to be too thin, and the residual bubbles in the pit will cause the coating to fail prematurely. Generally, the control roughness is preferably 1/10 of the thickness of the coating.
4. Ideal surface pretreatment effect
(1.) no grease (more important for waterborne coatings), no rust products (sometimes unrecognizable to the naked eye), no dirt;
(2.) a surface of the substrate having a certain roughness;
(3.) Add a layer of chemical conversion film (such as: phosphating film, coupling agent, phytate film, etc.), transition layer (aluminum alloy type),Anodized film, etc.
The above is about the "metal surface treatment in the painting process" related content, then, I will introduce the "influencing factors of metal surface pretreatment" related information, welcome to pay attention to us to get updated information!