The study on the corrosion mechanism of protective ternary ZnFeMo alloy coatings deposited on carbon steel in 0.5 mol dm–3 NaCl solution. (1st July 2018)

• Record Type: Journal Article
• Authors: Winiarski, J.; Tylus, W.; Lutz, A.; De Graeve, I.; Szczygieł, B.
• Is Part Of: Corrosion science. Volume 138(2018)
• Page Start: 130
• Page End: 141
• Publication Date: 2018-07-01
• Subjects: A. Metal coatings -- A. Alloy -- B. XPS -- B. EIS -- C. Electrodeposited films -- C. Passive layers; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2018.04.011
• Languages: English
• ISSNs: 0010-938X

Abstract

Graphical abstract: Highlights: The mechanism of oxidation of ZnFeMo coatings in the presence of chloride ions. Slow transformation of ZnO and Zn(OH)2 into Zn5 (OH)6 (CO3 )2 and Zn5 (OH)8 Cl2 ·H2 O. Oxidation of molybdenum in MoO2 to Mo(VI) species: MoO3 and MoO(OH)2 . The fact that this is the first SVET measurement on a zinc alloy coating with Mo. Even under aggressive conditions the corrosion activity of the coating stays low. Abstract: The passive layer on ZnFeMo coating (7.6 at.% Fe, 1.6 at.% Mo) became damaged in 0.5 M NaCl solution, as shown in ionic current density maps that were observed during 10 h of exposure. The ZnO and Zn(OH)2 slowly transformed into Zn5 (OH)6 (CO3 )2 and Zn5 (OH)8 Cl2 ·H2 O. At the same time, MoO2 transformed to MoO3 and MoO(OH)2 . The barrier properties of the layer of corrosion products deteriorated so the charge transfer resistance decreased from 13 to 7.4 kΩ cm 2 and the double layer capacitance increased from 4.5 to 62 μF cm –2 after 0.5 h and 10 h exposure, respectively.