How To Prepare A Surface For Thermal Spray Coating: A 5-Step Guide

Thermal spray coating is a popular method used in various industries to protect surfaces from wear, corrosion, and other forms of damage. However, to ensure the effectiveness of thermal spray coating, it is crucial to properly prepare the surface before applying the coating. In this article, we will provide you with a 5-step guide on how to prepare a surface for thermal spray coating.

Step 1: Clean the Surface

Before applying thermal spray coating, it is essential to clean the surface thoroughly to remove any contaminants such as dirt, oil, grease, or rust. These contaminants can interfere with the adhesion of the coating, leading to a weak bond and potential coating failure. There are several methods for cleaning the surface, including solvent cleaning, abrasive blasting, and chemical cleaning. Solvent cleaning involves using a solvent to dissolve and remove contaminants from the surface. Abrasive blasting, such as sandblasting or shot blasting, uses abrasive materials to physically remove contaminants. Chemical cleaning involves using chemical solutions to dissolve and remove contaminants from the surface.

Step 2: Remove Oxides and Scale

After cleaning the surface, the next step is to remove any oxides or scale that may be present. Oxides and scale can form on metal surfaces due to exposure to high temperatures or environmental factors. They can prevent the thermal spray coating from adhering properly to the surface, leading to coating failure. To remove oxides and scale, mechanical methods such as grinding, sanding, or wire brushing can be used. Chemical methods, such as pickling or acid etching, can also be used to dissolve and remove oxides and scale from the surface.

Step 3: Surface Roughening

To ensure good adhesion of the thermal spray coating, the surface must be roughened to create a mechanical bond between the coating and the substrate. Surface roughening can be achieved through methods such as grit blasting or abrasive blasting. Grit blasting involves propelling abrasive particles onto the surface at high speeds to create a rough surface profile. Abrasive blasting, such as sandblasting or shot blasting, uses abrasive materials to roughen the surface. The roughened surface provides an anchor for the thermal spray coating, improving adhesion and durability.

Step 4: Preheating the Surface

Preheating the surface before applying the thermal spray coating can help improve the coating's adhesion and reduce residual stresses in the coating. Preheating the surface can also help to reduce the effects of thermal shock during the coating process. The temperature and duration of preheating will depend on the type of material being coated and the specific requirements of the coating process. In general, preheating the surface to a temperature slightly below the melting point of the coating material is recommended for most applications.

Step 5: Masking and Taping

Before applying the thermal spray coating, it is essential to mask off any areas that do not require coating. Masking and taping help to protect these areas from overspray or coating buildup, ensuring a clean and precise finish. Masking materials such as tape, paper, or liquid masking agents can be used to cover surfaces or components that do not need to be coated. Careful masking and taping are crucial to achieving a high-quality thermal spray coating with clean edges and precise coverage.

In conclusion, proper surface preparation is essential for the success of thermal spray coating. By following the 5-step guide outlined in this article, you can ensure that the surface is clean, free of contaminants, roughened for good adhesion, preheated for optimal coating application, and properly masked for a clean finish. By taking the time to prepare the surface correctly, you can achieve a durable and high-quality thermal spray coating that will protect your components and equipment for years to come.