This book presents the key concepts in  electrochemistry applied to metal corrosion, such as processes at the metal-medium boundary and the role of electrochemical cells in redox reactions. It covers thermodynamic principles, including Gibbs energy, the Nernst equation, Pourbaix diagrams, and polarization curves, essential for predicting electrode reactions. The chapters classifies corrosion types like electrochemical, pitting, crevice, and intergranular, with a focus on mechano-chemical corrosion in welded structures. Visual diagrams simplify complex concepts, while real-world examples illustrate common "metal-corrosive environment" systems. The text addresses welding impacts, such as microstructural changes and residual stresses, and their synergy with corrosion, alongside methods for evaluating corrosion resistance, acoustic emission techniques for monitoring welded structures, and the potential of artificial neural networks in identifying corrosion damage. Emphasizing active corrosion protection methods, it uses underground pipelines as a case study to explore corrosion mechanisms, making it an invaluable resource for students, postgraduates, and professionals in welding, corrosion, and metal protection fields.