Title
Corrosion resistance of Zn-Co-Fe alloy coatings on high strength steel
Author
Lodhi, Z.F.
Mol, J.M.C.
Hovestad, A.
't Hoen-Velterop, L.
Terryn, H.
de Wit, J.H.W.
TNO Industrie en Techniek
Publication year
2009
Abstract
The corrosion properties of electrodeposited zinc-cobalt-iron (Zn-Co-Fe) alloys (up to 40 wt.% Co and 1 wt.% Fe) on steel were studied by using various electrochemical techniques and compared with zinc (Zn) and cadmium (Cd) coatings in 3.5% NaCl solution. It was found that with an increase in Co content in the coating the open circuit potential (OCP) became more positive than that of the zinc coating. For Co contents higher than 30 wt.% the OCP shifted close to that of Cd, but still remained electronegative to the steel substrate. Zn-Co-Fe coatings with ≥ 30 wt.% Co + 1 wt.% Fe are nano-crystalline in nature and show superior corrosion resistance as compared to the Zn, low Co content Zn-Co-Fe and Cd coatings. During longer immersion, Zn-Co-Fe alloys with 34-40 wt.% Co became more noble to steel due to dezincification of the surface but the corresponding corrosion current density decreased. The corrosion resistance determined by the electrochemical techniques are confirmed by salt spray testing showing the superior corrosion resistance for Cd and high Co content Zn-Co-Fe alloys and poor performance of alloys with lower Co contents and pure Zn. © 2008 Elsevier B.V. All rights reserved.
Subject
Materials
Cadmium
Corrosion resistance
Electrochemical evaluation
Salt spray
Zinc alloys
Alloys
Cadmium alloys
Coatings
Cobalt
Corrosion
Corrosion resistance
Iron alloys
Metallic compounds
Open circuit voltage
Protective coatings
Sodium chloride
Steel
Transition metals
Zinc plating
Alloy coatings
Circuit potentials
CO content
Corrosion currents
Corrosion properties
Electrochemical evaluation
High strength steel (HSS)
Sodium chloride (NaCl) solution
Steel substrates
Superior corrosion
Zinc coatings
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TNO identifier
241418
ISSN
0257-8972
Source
Surface and Coatings Technology, 203 (10-11), 1415-1422
Document type
article