Characterization and Corrosion Resistance of Galvanized Steel/Passivation Composite/ Polyurethane Paint Systems

Abstract

The corrosion performance of electrogalvanised steel sheets pre-treated with a Cr 3+ or Cr +6 -based conversion layer and then covered with 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 dispersion type was the formulation variable. The pigment was TiO 2 (rutile) with a PVC value of 10. Before and after the immersion in 0.05 M NaCl (pH 5.70) or 0.1 M Na 2 SO 4 (pH 6.36) solutions, replicates of the different samples were subjected to standardized tests (porosity, gloss and color, hardness, flexibility). During the immersion, blistering and rusting degrees were evaluated through periodical visual inspections, while the coated steel performance was monitored by Electrochemical Impedance Spectroscopy (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 Original Research ArticleBritish Journal of Applied Science & Technology, 4(6): 853-878, 2014 854 standardized tests results, it was concluded that the studied polyurethane-based polymeric films applied on pretreated electrogalvanised steel provided a very effective protection against corrosion as a result of their excellent barrier properties.

Comparison of Friction Properties of GI Steel Plates with Various Surface Treatments

“…Podjuklova et al [53] proved the enhanced short-term corrosion protection of a transparent coating system containing particles of zinc compounds applied on steel sheets for enameling. Sarli et al [54] applied polyurethane-based polymeric films on pretreated electrogalvanized steel which provided very effective protection against corrosion as a result of their excellent barrier properties. Gao et al [55] studied acrylic coatings composed of modified MoS 2 nanosheets successfully prepared on the surface of galvanized sheets.…”