Electrochemical properties and Morphology evaluation of the Lanthanum based Conversion Coating on Cold rolled steel

Document Type : Research Article

Authors
Masoud Nouri 1
Milad Bijani 2
Ali Asghar Sarabi 2
Hossein Eivaz Mohammadloo 2
1 School of Materials, University of Manchester, Manchester
2 Faculty of Polymer Engineering & Color Technology, Amirkabir intensity of Technology, Tehran
/amnc.2015.4.14.1
Abstract
In this search, conversion coating was applied on cold rolled steel try immersing specimens in a solution including La(NO3)3, and the effect of immersion time has been investigated. Electrochemical properties of the formed oxide layer were assessed Electrochemical Impedance Spectroscopy (EIS) and DC Polarization measurements. The morphology of the surface of wild rolled steel treated by conversion coating at different immersion times was studied by Field Emission Scanning Electron Microscopy (FE-SIM). The EIS and SEM results showed that better corrosion resistance (2.5 kΩ.cm2) along with a more uniform surface profile was achieved after 5 min immersion in the conversion coating bath. On the other hand, the coatings, which were formed by immersion in the rare-earth salt containing solution, significantly reduced the dissolution of La oxides and deteriorated the substrate after 50 min. Adhesion of epoxy organic coating to the untreated and La conversion-coated CRS was evaluated try pull-off method and results revealed the positive performance of La conversion coating.
Keywords
Conversion coating
Lanthanum Nitrate
polarization
Electrochemical Impedance Spectroscopy (EIS)
Field Emission Scanning Electron Microscopy (FE-SEM)