Corrosion in welded structures isn’t just rust — it takes many forms, each with unique causes and risks. Welds often corrode faster than base metal because of differences in microstructure, composition, and residual stress. The main types include general corrosion, galvanic, crevice, pitting, intergranular attack, stress corrosion cracking, and microbiologically induced corrosion. Understanding these forms is critical because each requires a different prevention strategy, from material selection to welding technique and protective coatings. By learning how corrosion works, companies can extend equipment life, avoid failures, and save significant costs.