Scale and oxide layer residue
Thermal oxide films left on the weld or base metal that reduce corrosion resistance and indicate inadequate post-weld cleaning.
Physical-Chemical Mechanism of Action
Scale and oxide layer residues are formed by thermal oxidation during the welding process. When steel is heated, a thin, heat-resistant protective film of silicon dioxide (SiO2) or chromium dioxide (Cr2O3) forms, depending on the filler content. This film cannot be completely removed during cooling and remains as residue on the weld or the base material.
Metallurgical Relevance & Welding Risks
These residues reduce the corrosion resistance of the weld, as they provide an entry point for water and air-borne substances. They can also impair mechanical properties, especially hardness and toughness. In heavily loaded applications, this can lead to premature failure of the weld.
Workshop Practice & Action Instructions
To minimize scale and oxide layer residues, careful post-treatment is essential. This includes removing residual dirt and applying a corrosion-protective coating on the weld. In heavily loaded applications, a post-weld treatment step such as tempering or a tempered heat treatment may be recommended to improve mechanical properties and increase corrosion resistance.