What Is a Surface Preparation?
Surface preparation is a general term used to describe the process of cleaning the surface to be coated by removing black marks, rust, and dirt from the surface of iron parts, and the degree to which the surface has been cleaned and adjusted.
Blackened skin, rust, and adhered dirt on steel surfaces are removed using wire brushes, disk sanders, blasting, and other methods. The extent of removal depends on the method and tools employed, and the degree of removal is indicated by an index ranging from Type 1 to Type 4 surface preparation.
Purposes of Surface Preparations
There are two purposes for surface preparations. The first is to adjust the surface to be painted, and the second is to improve the adhesion of the paint.
- Preparation of Painted Surfaces
Before applying the paint, black film (two black spots generated when steel is heated), rust, salt, moisture, dust, and other adhering matter are removed as much as possible to ensure the paint film adheres firmly to the surface to be coated. - Improvement of Paint Adhesion
To improve the adhesion of the paint film, the surface to be coated is made uneven. The uneven surface (anchor pattern) increases the surface area compared to a smooth surface, allowing the paint to penetrate into the micro-unevenness of the surface to fix the paint film and make it difficult to peel off. This method is called the anchor effect.
How to Select Surface Preparations
There are four types of surface preparation, each of which requires a different level of precision and tools.
- Type 1 Surface Preparation
Surface condition: All black film, rust, and stains are completely removed, and 95% of the surface area is free of any obvious residual material.
Treatment method: Shot blasting, sandblasting, etc. - Type 2 Surface Preparation
Surface Condition: Completely removed from the surface, leaving the completely adhering black skin, rust, and stains, with at least 2/3 of the surface area free of distinct residuals.
Treatment method: Applied with a disk sander, wire wheel, grinder, etc. - Type 3 Surface Preparation
Surface Condition: Rust, old paint film, and stains are removed, and the surface has a faint metallic luster.
Treatment method: Wire brush, scraper, etc. - Type 4 Surface Preparation
Surface condition: Rust and dirt are removed, leaving an active film (a coating film that still adheres to the substrate and functions as a protective film even if the aesthetics of the coating film are compromised).
Treatment method: Wire brush, scraper, etc.The degree of surface preparations by surface preparations are general term and is not defined by any standard, but the following is a comparison of the degree of surface preparations by surface preparations and other standards) and SIS (Svenska Standard SIS 05 5900 Swedish Standard).
Surface preparations for Type 1: Sa3/Sa2 in ISO and SIS, SP-5/SP-10 in SSPC.
Surface preparations for Type 2: St3 in ISO and SIS, SP-3 in SSPC.
Surface preparations 3, St2 in ISO and SIS, SP-3 in SSPC
No equivalent for Type 4 surface preparations