Comments to
- M.M. Attar, J.D. Scantlebury
- Polyaniline as a possible inhibitor for the corrosion of mild steel
J. Corr. Sci. Eng., Vol 1, paper 8
Date: Fri, 13 Feb 1998 17:02:30 BST
Sender: CORROS-Request @listserv.rl.ac.uk>
From: David Scantlebury @FS1.CP.UMIST.AC.UK>
Subject: what is passivity?
To: Multiple recipients of list CORROS-L @LISTSERV.RL.AC.UK>
Since Mr. Wessling was so kind as to advise me to read the literature,
(especially his publications) in the field of polyaniline, I came
across one of his recent publications with an interesting scientific
dilemma which I would like to share.
Corrosion protection of Mild Steel by Coatings containing polyaniline;
Lu, Elsenbaumer and Wessling, Synthetic Metals, 71, 2163-2166, (1995)
In this paper they first coated mild steel with neutral or doped
polyaniline, followed by an epoxy top-coat. They drilled a hole down
to the steel. The first experiment they carried out was a measurement
of potential versus time, in 0.1N HCl and 3.5% NaCl.
I would remind Mr Wessling of the data he obtained for the NaCl
solutions with and without the polyaniline. Without the polyaniline
potentials varied from -0.64V SCE to -0.62V SCE after 8 weeks.
With the neutral polyaniline, potentials started at -0.88V SCE at 1h
and moved to -0.82V after 8 weeks
The doped polyaniline, started at -0.87V SCE and moved to -0.85V SCE
after 8 weeks.
Looking at Pourbaix, it is clear that at these potentials in neutral
sodium chloride, it cannot be claimed that the steel was passive and
that this conclusion drawn by Wessling in the final and abstract
sections of the paper is wrong.
David
David Scantlebury, Corrosion and Protection Centre, UMIST,
PO Box 88, Manchester, M60 1QD, UK, email scantlebury@umist.ac.uk,
http//www.cp.umist.ac.uk/cpc/staff/jds-profile.htm
phone (44)161-200 4841 fax 161-200 4865 home phone 161-434 6832
