A welder is attempting to repair a cast iron machine part that is heavily contaminated with oil and grease. The best approach to prepare the parent metal for welding is:

Question: A welder is attempting to repair a cast iron machine part that is heavily contaminated with oil and grease. The best approach to prepare the parent metal for welding is:

Answer options:

• Simply brush the surface with a wire brush. ✅ Thoroughly clean with solvent, then grind to remove impregnated contaminants, followed by preheating.
• Apply a high heat immediately to burn off the contaminants.
• Weld directly over the contaminated area at a higher amperage setting.

Correct answer: Thoroughly clean with solvent, then grind to remove impregnated contaminants, followed by preheating.

Explanation: Heavily contaminated cast iron requires thorough cleaning. This involves dissolving surface contaminants with a solvent, followed by grinding to remove any contaminants that may have impregnated the porous cast iron surface. Preheating further helps to drive out any remaining volatile substances and reduces the risk of cracking. Wire brushing alone is insufficient, burning off contaminants can lead to porosity, and welding over contamination is unacceptable.