Which method is often used to prepare surfaces by removing oxide layers before Magnetic Particle Testing?

Preparing surfaces by removing oxide layers is crucial to ensure effective Magnetic Particle Testing (MPT), as any contaminants can mask defects and lead to inaccurate results. Sanding or grinding is a mechanical method that not only removes oxide layers but can also smooth the surface, thereby enhancing the adherence of the magnetic particles. This mechanical abrasion creates a fresh surface that is free from impurities, allowing for better visibility of surface defects.

In contrast, while other options such as washing with water, applying a chemical solution, or using a high-pressure air blast may clean a surface to some extent, they are not as effective at uniformly removing oxide layers and surface contaminants. These alternatives may leave residues or may not penetrate deeply enough to eliminate tightly adhered oxides. Therefore, sanding or grinding is the most reliable method for preparing surfaces prior to MPT, ensuring that the oxide layers do not interfere with the test results.