Die Korrelation der Witterungseinflüsse im Hafen von Chennai (Bucht von Bengalen, Indien) zu Salz-Sprüh Tests mit elektrochemischer Impedanz Spekroskopie in Bezug auf Lacksysteme

Abstract

Wire-brushed mild steel panels were coated with three coating systems: vinyl, epoxy-urethane and polyurethane systems. A set of panels was exposed in a salt-spray chamber for 720 hours and another set of panels at Chennai Port for 18 months. The panels were then removed from the site, and salt-spray chamber and AC impedance measurements were conducted in a 0.5M sodium chloride solution. The photographs of the panels exposed in the salt-spray chamber and at Chennai Port indicated that all the panels in the Port site had higher corrosion spots and blisters than that in the salt-spray chamber. The AC impedance observations of both sets of panels indicated that the resistance offered by the vinyl and epoxy-urethane systems were in the order of 109ohmcm2, whereas in the polyurethane system, the resistance was in the order of 105 to 104ohmcm2. Thus better correlations were obtained between the AC impedance and salt-spray tests, and with field exposure data for the epoxy-urethane and vinyl systems, but a slight variation of this correlation was observed in the case of the polyurethane system. Thus it was concluded that vinyl and epoxy-urethane coating systems should be used as maintenance coating systems for mild steel surfaces for the corrosive atmosphere prevailing in the Chennai Port environment.