CHARACTERIZATION AND CORROSION RESISTANCE OF GALVANIZED STEEL/PASSIVATION COMPOSITE/BARRIER PAINT SYSTEMS

C.R. TOMACHUK; C.I. ELSNER; A.R. DI SARLI

British Journal of Engineering and Technology

Association of Academic Research

Lugar: New York; Año: 2014 vol. 4 p. 853 - 878

2326-425X

The corrosion performance of electrogalvanised steel sheets pre-treated with a Cr3+ or Cr+6-based conversion layer, and then covered with a polyurethane-waterborne topcoat paint has been studied. The pre-treated metallic panels were coated with one of the three tested polyurethane (PU) topcoat paints, in which the emulsion type was the formulation variable. The barrier pigment was TiO2 (rutile) with a PVC value of 10. Before and after the immersion in 0.05 M NaCl or 0.1 M Na2SO4 solutions, replicates of the different samples were subjected to standardized tests (porosity, gloss and colour, hardness, flexibility). During the immersion, blistering and rusting degrees were evaluated through periodical visual inspections, while the coated steel performance was monitored by EIS measurements. Initial (dry) and final (wet) paint adhesion was also determined. EIS data were interpreted and discussed in terms of the time dependence of the electrical (paint coating) and electrochemical (steel substrate) parameters associated with interfacial processes describing the metal/paint system deterioration. According to the electrochemical properties, visual inspection and standardized tests results, it was concluded that the studied polyurethane-based polymeric films applied on pre-treated electrogalvanised steel provided a very effective protection against corrosion as a result of their excellent barrier properties