The right sequence of abrasives can successfully achieve a seamless appearance when finishing welded carbon steel parts.
Depending on the paint system, available tools, and desired outcomes, there are multiple ways and products to choose from in achieving a carbon steel finish that can be painted or coated. The following process is recommended as an excellent starting point.
For medium paint or coatings (2+ mils, metal enclosures, general fabricated parts), Use a right angle sander, level the weld with a 3M Cubitron™ II fibre disc 982C, grade 60+. Choose a finer grade for smaller welds and a coarser grade for larger welds. Use 3M™ Red Ribbed Back-up pad to optimize performance.
Refine the finish with Scotch-Brite™ surface conditioning (SC) disc, grade A coarse (A-CRS) with same back-up pad as Step 1.