The statement 'You should never use brake cleaner to clean a weld because welding over it can create extremely dangerous phosgene gas' is:

• A. False
• B. True
• C. Sometimes true
• D. Not enough information

Answer: (B)

Chlorinated solvents used to clean welds can form phosgene when exposed to welding heat. Brake cleaner often contains chlorinated solvents like methylene chloride. When you weld, the intense heat and arc break down these solvents on the metal surface, and phosgene gas (a highly toxic compound) can be generated. Because welding over residues from brake cleaner can release this dangerous gas, it’s safer to avoid brake cleaners in the weld area. Use a non-chlorinated degreaser or soap and water, and ensure the surface is fully dry and free of solvents before welding, with good ventilation.