The discipline “APPLICATION OF SURFACE SCIENCE AND SURFACE ENGINEERING IN WELDING AND JOINING deals with the assessment of the wetting of a liquid material in a solid surface. It is a fundamental subject to understand of practical problems during and after welding or joining. In fact, to joint two or more solid surfaces by a liquid material is the fundamental issue in welding and joining process by fusion. The main objective of the course is to provide participants with an introduction to surface thermodynamics with emphasis in welding and joining of materials, defining wetting, and spreading of a liquid over a solid; deduction of Young Equation for free wetting; definition of Electrowetting; Young-Lippmann equation deduction and methods of surface tension measurement. The course ends with examples from practical application cases, which links the wetting and spreading theory to welding engineering practice. During each class there will be lectures with relevant classroom exercises