CHARACTERIZATION OF ANTI-CORROSION TRIAZOLE FILM By ...

J.Sc. Tech ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ ــــــــــــــــــــــــــــــVol.
10(2) 2009
I (mA)
-2.5 -2 -1.5 -1
0
-0.5
-0.0001
0 0.5 1
E (V)
Fig. (2): CV for Zn in sea water + MTRA
Table (1): Anodic and cathodic peaks from cyclic-voltammograms
Compound Anodic Peak Cathodic Peak
E anodic (mV) I anodic (mA) E
(mV)
cathodic I cathodic (mA)
Zn + Sea water 378 20.48 -1030 -76.38
Zn +Sea water + MTRA …… ….. …… ……
The SEM photographs for the corroded zinc surface and the surface after
addition of inhibitors are shown in figures 3 and 4 respectively. The
inhibitors function by adsorption on metal surface forming a film. The
evidence for the presence of the film on zinc surface comes from SEM
photographs where fine surface film is seen on the surface exposed to sea
water containing the inhibitor (Fig.4) when compared to the surface exposed
to sea water without inhibitor (Fig. 3). Figure (3) shows large grained
morphology with deep terraces while the films obtained in the presence of
inhibitors show smooth small grained surface [Taha, 2002]. A previous study
[Ravichandran et al, 2005] with SEM technique supported the formation of a
compact surface film on brass surface in presence of the triazole inhibitor.
Kunitsugu [Kunitsugu, 2001] suggested that the inhibitors formed protective
films of Zn (II) salts or complexes on zinc surface together with zinc
hydroxide and oxide to prevent corrosion. Mercaptotriazole was found to be
95
0.0005
0.0004
0.0003
0.0002
0.0001
-0.0002
-0.0003
-0.0004
-0.0005