A Rapid Assessment of Non-Chromate Primers for Zn/Ni Plated Steel By Electrochemical Techniques
Authors: Zhang Weilong , Kryzman Mike A , Jaworowski Mark R , Zafiris George S 
Published: February 2020

The pace of non-chromate coating developments is largely governed by a time-consuming coating evaluation process for its anti-corrosion properties. The most common accelerated test protocols for coating evaluation: (1) ASTM B117 Salt Spray, (2) ASTM D 5894 Cyclic Salt Fog/UV exposure, or (3) SAE J2234 Cyclic Corrosion test. Those tests are not only very time-consuming, but also do not give quantitative information about coating degradation process.

There is an increasing interest in rapid assessment methods for practical applications which provide an early indication of long-term coating performance. Several EIS-based accelerated test protocols1-7 have been developed, including (1) thermal cycling testing1 by impedance measurement at high temperature, (2) rapid electrochemical assessment of paint (REAP)2-4 by impedance measurement and cathodic disbonding tests on two identical samples, and (3) the AC/DC/AC procedure5-7 by combining impedance tests before and after a DC disbonding on the same sample. Unfortunately, above test protocols are not guaranteed to work for every coating in every environment.

In this work, we propose a different electrochemical stress cycle test protocol, in combined with coating damage tolerance technique that aims to determine quantitatively the galvanic functionality of Zn/Ni layer in non-chromate primed steel sample. The effect of coating damaged size is also investigated. It is assumed that the lowest dissolution of Zn/Ni layer, the longest lifetime of the non-chromate primer. The new test protocol has been validated as a useful method for determining a performance ranking of a series of non-chromate primers in very short times, comparing it with other different evaluation methods including salt fog test per ASTM B1178.

Acknowledgements

This work was performed under United Technologies Corporate R&D funding.

References

G.P. Bierwagen, L. He, J. Li, L. Ellingson, and D.E. Tallman, "Studies of a new accelerated evaluation method for coating corrosion resistance—thermal cycling testing." Progress in Organic Coatings 39.1 (2000): 67-78.

M. Kendig, S. Jeanjaquet, R. Brown, and F. Thomas, "Rapid Electrochemical Assessment of Paint," J. Coatings Technology, 68 No. 863, 39 (1996).

J.J. Suay, M.T. Rodriguez, R. Izquierdo, A. H. Kudama, J.J. Saura, "Rapid Assessment of Automotive Epoxy primers by Electrochemical Techniques" J. Coating Technology, 75 No. 946,103 (2003).

 M. Poelman, M. G. Olivier, N. Gayarre, J. P. Petitjean, "Electrochemical Studies of Different Aging Tests for the Evaluation of a Cataphoretic Epoxy primer on aluminum", Progress in Organic Coatings, 54: 55-62 (2005).

J. Hollaender, E. Ludwig, S. Hillebrand, Proc. 5th International Tinplate Conference, London, 1992, pp 300ff.

 J. Hollaender, C.A. Schiller, W. Strunz, Food additives and contaminants, 1999, Vol 14, No.6-7, pp 617ff.

 J. Hollaender, C.A. Schiller, W. Strunz, Proc. EIS 2001, Marilleva-Italy, 2001.

M. Jaworowski, M. Kryzman, M. Manzini, R. Panza-Giosa, G. Zafiris, W. Zhang, “Chrome-Free Paint Primer for Zn/Ni Plated High- Strength Steel”, Presentation at 2014 ASETSDefense  Workshop,Fort Myer, VA  2014 .