What material must be avoided as a substitute to aluminum oxide abrasive cloth and why?

• A. Sandpaper
• B. Aluminum oxide paper
• C. Garnet paper
• D. Silicon carbide paper, because it is sharp and the individual grains can penetrate steel surfaces

Answer: (D)

When prepping steel surfaces, you want an abrasive that removes contamination and creates a clean, uniform finish without causing deep damage or leaving grit behind. Silicon carbide is much harder and sharper than aluminum oxide, so its grains can cut into the steel rather than just abrade it. That leads to deep scratches, micro-pits, and possible grit embedding, all of which become initiation points for corrosion and can interfere with coating adhesion. Because of this, silicon carbide paper should be avoided as a substitute for aluminum oxide abrasive cloth. The other options are generally more suitable for metal surface prep and are less likely to create those damaging defects.