Surface preparation is a critical step in the metal finishing process greatly impacting the quality, durability, and appearance of the final product...
Whether you are anodizing or applying any type of coating, plating, or other finishing, an ounce of preparation is worth a pound (or more!) of cure.
This surface prep step is essential because it ensures that the surface is free of contaminants, rust, or previous coatings that could interfere with adhesion and affect the finish’s durability. The goal is to create a surface that is clean, smooth, and ready to accept the final coating. There are several different ways to accomplish this, from sandblasting to titanium etching, each tailored to specific requirements and the material at hand.
At AOTCO, we recognize that the key to any successful metal finishing project is rooted in thorough and deliberate surface preparation. That’s why we are committed to employing meticulous, strategic surface preparation methods that guarantee the highest quality outcomes for every project.
Any kind of surface contaminant can compromise the quality of the final metal finishing. Understanding these contaminants can help you select the appropriate surface preparation methods.
Oils and grease are common contaminants that originate from manufacturing processes or handling. These substances can create a barrier on the metal surface, preventing coatings and finishings from properly adhering. They need to be removed using solvents, detergents, or alkaline cleaning methods to ensure a clean surface.
Chlorides and acids are corrosive agents that can be present due to environmental exposure or chemical processes. These contaminants can cause under-film corrosion, leading to coating failure. Removing chlorides and acids typically involves washing with water or using neutralizing agents.
Mill scale, a layer of iron oxides that can form during hot rolling of steel, and rust from oxidation, are common on untreated steel surfaces. Both must be thoroughly removed to expose bare metal in order for proper adhesion. Abrasive blast cleaning is a common method used to remove mill scale and rust effectively.
Loose coatings and corrosion products from previous treatments can interfere with the new coating's adhesion. Methods like hand tool cleaning, power tool cleaning, or abrasive blasting can remove these alternative coatings and ensure the new coating bonds properly with the substrate.
Other foreign materials, such as dust and debris, can lead to blistering and other coating defects. These contaminants are typically removed through water jetting, vacuum cleaning, solvent cleaning, and other methods to ensure a pristine surface.
Surface contaminants have significant adverse effects on coating adhesion and overall performance.
There are several different ways to tackle removing various types of contaminants. The most common techniques can be categorized as mechanical cleaning, chemical cleaning, and blast cleaning.
Let’s look at the most common methods of surface preparation and the pros/cons of each.
Blast cleaning, like sandblasting or grit blasting, involves propelling a stream of abrasive particles against a surface under high pressure. This method is highly effective for removing dirt, rust, mill scale, and other contaminants, creating a clean surface suitable for coating adhesion.
Manually or mechanically removing loose contaminants can be done with hand or power cleaning tools, clearing the metal surface of rust, mill scale, and old coatings.
Chemical cleaning involves using various chemicals to remove contaminants from the metal surface.
Each step in the surface prep process helps ensure the metal surface is clean, free from contaminants, appropriately textured, and ready to accept the chosen coating material. Not every step is required: it depends on the metal, the contamination, and the final finishing.
Cleaning is the initial step in surface preparation. It involves removing contaminants such as dirt, grease, or oil from the metal surface. For light contamination, wiping with a clean cloth or using solvent cleaners can suffice. Heavy contamination may require more aggressive methods like blasting or chemical cleaning.
Degreasing focuses specifically on removing oils and greases from the metal surface, common contaminants that can compromise adhesion. Solvents, alkaline cleaners, or acid cleaners that are tailored to the type of metal and the nature of the contamination may be needed.
Sanding or grinding is employed to smooth out imperfections or roughness on the metal surface or to remove particularly tough contaminants. Make sure to choose the appropriate abrasive material based on the metal type and the extent of imperfections.
Surface etching alters the metal surface chemically to create specific textures or patterns. This enhances both decorative and functional aspects of the surface, which is crucial for applications where aesthetics or specific surface characteristics are desired. Titanium etching is one of the most common examples of this process.
The final step involves applying the chosen coating material or finishing to the prepared metal surface. This may include plating, anodizing, painting, or other processes based on the desired finish and application requirements.
After the finishing application, certain post-process treatments may be necessary to ensure the longevity and performance of the finished metal product. This can include chem film (conversion coating or chromate), custom masking, engraving, or laser marking.
Partnering with AOTCO for your surface preparation needs ensures that you receive high-quality results and a collaborative, efficient experience – at every stage of the metal finishing process.
Whether your project requires basic cleaning or intricate surface preparation, AOTCO is ready to provide reliable, innovative, and effective solutions tailored to your needs. Contact us today to learn more.