R. Devesa, S. Urréjola

Centro Universitario de la Defensa en la ENM (SPAIN)
Electrocoating is an anticorrosive protection treatment widely used in automotive. It consists of creating a polymerization layer by electrodeposition by deposition of the painting on the substrate by the action of electric current.

The main functions of electrodeposition are:
• To guarantee the permanence of the phosphate coating (ensure anticorrosion).
• To eliminate the inherent defects of the metal substrate (scratches, micropores, roughness ...).
• To prepare the substrate for the deposition of the subsequent layers for a durable finish.

The physico-chemical principle of electrocoating is the displacement of charged particles in an electric field. The scheme of the process occurs as follows: The automotive, connected to the negative pole or cathode, is introduced into a electrocoating paint bath, whose tub is connected to the opposite pole, the positive or anode. Thus, by means of the electric current, paint is deposited on the automotive. The thickness of the layer depends mainly on the applied voltage, since the layer that is deposited does not conduct the electric current, so that the electrical effect ceases when the layer reaches a certain thickness. It also depends on the immersion time, the concentration of the bath and the electric current. With an immersion time of between 2 and 4 minutes, the thickness values range between 18 and 20 microns.

The main goal of this experiment is to establish the basic foundations of electrocoating, surface treatments and corrosion, which are topics covered in an Engineering Materials course. Students have to undertake experiments in a laboratory as part of the course. Lab works should give to the students, “hands on” experience in the use of equipment and experimental techniques and also allow to the students make links between the object/event world and the theory/model world. The main goals as engineering educators should include equipping students with problem-solving, communication, teamwork, self-assessment, change management and lifelong learning skills. In particular, the study considers the application of an electrocoating to a metal substrate to mimic the coating in automotive for minimize corrosion, so students will relate “real world” into an otherwise theoretical education. The main laboratory skills developed under the framework of this course will be problem-working, communication and teamwork. So, a sequential learning is proposed, where students will gain understanding in linear steps, with each step following logically from the previous one. This will make students to follow logical stepwise paths in finding solutions, strengthening their global thinking skills by relating each new topic with the things they already know.