Prohesion and outdoors tests on corrosion products developed over painted galvanized steel sheets without Cr VI species .

M. ZAPPONI; T. PÉREZ; C. RAMOS; C. SARAGOVI

CORROSION SCIENCE

Elsevier

Año: 2005 vol. 47 p. 923 - 936

0010-938X

Galvanized steel sheets pre-treated with a new product and then painted with a polyester topcoat without primer were submitted to Prohesion G-85 test (PT) and to outdoor marine exposure test (OT). The new product that replaces standard inorganic chromium pre-treatment + primer consists in a water based resin which applied directly to the properly cleaned metal substrate is then dried in place. This scheme sets aside Cr(VI) compounds which cause severe damages on human health. Goethite, lepidocrocite, magnetite, akaganeite and silicates were found in OT samples coinciding with the usual corrosion products obtained for conventional painting schemes (with Cr(VI)). Surprisingly in PT samples greigite was detected, showing that the new painting scheme is susceptible to microbiological corrosion. Goethite, lepidocrocite, pyrite, magnetite and akaganeite were also found.