The influence of molybdenum on the electrodeposition and properties of ternary Zn–Fe–Mo alloy coatings. (1st April 2016)

• Record Type: Journal Article
• Authors: Winiarski, J.; Tylus, W.; Krawczyk, M.S.; Szczygieł, B.
• Is Part Of: Electrochimica acta. Volume 196(2016)
• Page Start: 708
• Page End: 726
• Publication Date: 2016-04-01
• Subjects: Zn–Fe–Mo alloy coating -- electrodeposition -- EIS -- XPS -- anodic dissolution; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2016.03.027
• Languages: English
• ISSNs: 0013-4686

Abstract

Highlights: Ternary Zn–Fe–Mo alloy coatings for steel protection against corrosion. The content of Fe and Mo depends on the concentration of Na2 MoO4 in the bath. FeMo phase may appear in the presence of Mo and Fe in Zn–Fe–Mo alloy coatings. Passive layer enriched in Mo(IV) compounds forms on Zn–Fe–Mo alloy coating. Abstract: Ternary Zn–Fe–Mo alloy coatings, as a potential replacement for zinc coatings, were deposited from a citrate-sulphate solution. It has been shown that by varying the concentration of Na2 MoO4 in the plating bath in a range of 0.0025 − 0.05 mol dm −3 it is possible to obtain coatings containing from 0.4 to 2.7% at. Mo and from 2.8 to 7.6% at. Fe. It has been proved that molybdenum and iron do not form intermetallic phases with zinc. However, at higher Mo and Fe content the presence of oxidized molybdenum compounds in the coatings is possible. Among them the most probably are: FeMoO or Mo5 O7 (OH)8 . EIS measurements revealed that the ternary Zn–Fe–Mo alloy (7.6% at. Fe, 2.4% at. Mo) coating offer better corrosion resistance during 24 hours of exposure in NaCl solution than the Zn–Fe (1.7% at.) binary coating and pure Zn coating. The good protective properties of Zn–Fe–Mo coatings are due to the presence of a relatively thin (approx. 7 nm) passive layer enriched in molybdenum oxides and hydroxide compounds.