When should weld-through primers be applied in the welding process?

• A. After welding
• B. Before welding
• C. During grinding
• D. After heat treatment

Answer: (B)

Weld-through primer is applied before welding so the protective coating is already present at the joint as it’s formed. These primers are designed to endure the heat of welding just enough to stay around the weld edges, so the metal around the seam stays protected from corrosion once the weld cools. If the coating were put on after welding, the weld area would be exposed to moisture and salt, increasing the risk of rust where the two pieces are joined. Grinding and subsequent heat treatment are separate steps in the process and don’t provide the intended corrosion protection at the weld joint, which is why applying the primer beforehand is the best approach.