Question 66 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is C **Explanation for Option C (Wire brush):** A wire brush is the most appropriate hand tool among the choices for preparing metal surfaces with significant pitting. When a surface is pitted, corrosion products (rust) and scale accumulate deep within the depressions. A stiff wire brush (especially a cup-style or rotary wire brush driven by a power tool, though manual brushes also apply) physically abrades the surface, reaching into the microscopic crevices and pits to remove loose rust, paint remnants, and debris, ensuring that the surface is clean enough for primer adhesion. **Why the other options are incorrect:** **A) Hand scraper:** A hand scraper is designed for removing large, loose layers of paint or thick scale, or for smoothing surfaces. It relies on a flat or slightly curved blade and is ineffective at cleaning deep within the small, irregular contours of significant pitting. **B) Chipping hammer:** A chipping hammer (or scaling hammer) is used to remove heavy, thick layers of rust scale or weld spatter. While effective for bulk removal, it is too aggressive and imprecise for final surface preparation. Using a chipping hammer on pitted areas can further damage the underlying metal structure and will not leave a clean profile suitable for immediate priming. **D) Sandpaper:** Sandpaper (abrasive sheets) is excellent for light sanding, smoothing, or final feathering of edges, and preparing smooth surfaces. However, the paper backing and abrasive grit cannot effectively penetrate the depth and complexity of significant pitting to fully remove the trapped corrosion products. It will tend to skip over the pits, polishing the high points while leaving rust in the low points.