Surface Degradation and Protection
Faculdade de Ciências e Tecnologia
Departamento de Ciências dos Materiais
Teacher in charge
Rui Jorge Cordeiro Silva
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.
The evaluation is obtained through two tests for the students that obtained frequency by being assisting at labs and presenting the respective reports. The students with average grade, in the two tests, equal or superior to 9.5 (ranking of 20) have exemption from final exam. The student need to have in each evaluation test at least a grade of 7.0. The final classification will be a weighted average of the final exam grade or test''''''''''''''''s average (75%) plus lab reports (25%). To take into account the final exam grade or the test average grade should be at least 9.5 in a ranking of 20.