Evaluation of Corrosion Behavior of Galvanized Steel Treated with Conventional Conversion Coatings and a Chromate-Free Organic Inhibitor

• Main Authors: Laura A. Hernandez-Alvarado, Luis S. Hernandez, Sandra L. Rodriguez-Reyna
• Format: Article
• Language: English
• Published: Hindawi Limited 2012-01-01
• Series: International Journal of Corrosion
• Online Access: http://dx.doi.org/10.1155/2012/368130

Conventional weight loss tests and both DC and AC electrochemical techniques were used to study if an organic inhibitor containing an alkanolamine salt of a polycarboxylic acid can substitute toxic coatings as chromating and certain phosphating procedures in the protection of galvanized steel. The electrolyte used was a 0.5 M aerated NaCl solution. All tests gave concordant results, indicating that the chromate-free organic inhibitor does protect galvanized steel in this environment, even though the provided protection was less than that of the chromate conversion coating. It was observed that, after a moderate initial attack, the corrosion rate diminishes due to the appearance and growth of passivating corrosion products layers, mainly constituted by zinc hydroxychloride (Zn5(OH)8CI2⋅H2O) and two varieties of zinc hydroxide, among other crystalline compounds.