- Blister: A raised spot, usually on the surface of a tube or pipe, caused by expansion of gas in a cavity within the wall or diameter.
- Crack: A stress-induced separation of the metal which, without any other influence, is insufficient in extent to cause complete rupture of the material.
- Dent: A local change in surface contour caused by mechanical impact, but not accompanied by loss of metal.
- Gouge: Elongated grooves or cavities caused by mechanical removal of metal.
- Inclusion: Foreign material or non-metallic particles entrapped within the metal during solidification.
- Pit: A depression in the surface of metal occurring during its manufacture.
- Seam:An elongated discontinuity in metal caused by a blowhole or other defect which has been closed by rolling or forging mechanical but not welded.
- Lap: Fold of metal which has been rolled or otherwise worked against the surfaces of rolled metal, but has not fused into sound metal.
- Lamination: An internal metal separation creating layers generally parallel to the surface.