What is a crater crack and how can it be prevented?

• A. A type of surface corrosion that occurs after welding.
• B. A crack that forms at the end of a weld crater; prevent by completing the weld bead, blending the end, or adding a small fill or finishing pass.
• C. A crack that forms in the base metal away from the weld.
• D. A decorative feature at the weld toe.

Answer: (B)

Crater crack shows up at the end of the weld crater as the welding stops and the metal cools, creating a notch-like flaw where residual stresses are concentrated. The best way to prevent it is to finish the weld bead properly: complete the weld to the end, blend or feather the crater edge, or add a small fill or finishing pass to smooth the termination. This fills in the last portion of the weld, distributes heat more evenly, and removes the sharp termination that can crack as it cools.

So, finishing the crater by tying in the end and smoothing it out is the key protection. It’s not about corrosion, nor about cracks away from the weld, and it isn’t a decorative feature.