Surface Degradation and Protection
Rui Jorge Cordeiro Silva
Weekly - 5
Total - 92
Introduction to metallic corrosion forms. Dry and wet corrosion. Relative humidity. Classification of an atmosphere according to it HR value. The effect of HR on the corrosion mechanisms. Other types of atmospheres or corrosive environments. Dry corrosion. Thermodynamic principles (anodic and catodic reactions, equilibrium equations and understanding and use of Elligham diagrams). Corrosion mechanisms and oxide film grows processes and oxide types (p‑type and n-type). Effect of temperature, atmosphere composition and of alloying in the corrosion rate. Corrosion layers. Dry corrosion at low temperatures and the tarnishing effect. Wet corrosion. Electrochemical aspects (anodic and cathodic reactions in aqueous environment, electrochemical potential and electrochemical series for metals). Thermodynamic aspects (Nernst equation, construction and use of the Pourbaix diagrams).Corrosion kinetics evaluations (polarization curves, corrosion potential, corrosion current density and electrochemical testing methods). Wet corrosion forms (classification, recognizing , chemical mechanism and modes of prevention): uniform corrosion, galvanic corrosion, crevice corrosion, pitting, intergranular corrosion (sensitizing of austenitic stainless steels, weld decay, knife-line attack and exfoliation), dealloying or selective leaching (dezincification, graphitization and other examples), erosion-corrosion (including cavitation and fretting), stress-corrosion (including corrosion fatigue). Rust formation. Other forms of corrosion in metallic materials, such as microbiologic corrosion, and corrosion in no‑metallic materials (glass, plastic and concrete). Introduction to metallic coating, Surface preparation and general modes of application. Barrier effect and cathodic protection of a coating. Examples. Other modes of protection. Composition of paints and varnishes: binder, solvent, pigments and additives.General characteristics of the binders and their classification regarding its chemical nature. Solvents: types of solvents and their characteristics. Pigments and additives: chemical analysis, properties and applications. Constitution of a painting scheme and purpose of each of it’s constituents: selection of painting systems. Formulation and manufacturing of paints.Paint application. Testing on applied paint. Factors that affect the performance of the applied paint.
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