Progress in Organic Coatings 60 (2007) 320–327
Synthesis, characterization and corrosion protection properties of
poly(N-(methacryloyloxymethyl) benzotriazole-coglycidylmethacrylate) coatings on mild steel
A.P. Srikanth a , S. Nanjundan b , N. Rajendran a,∗
a
b
Department of Chemistry, MIT Campus, Anna University, Chennai 600044, India
Department of Chemistry, CEG Campus, Anna University, Chennai 600025, India
Received 2 March 2007; received in revised form 25 July 2007; accepted 1 August 2007
Abstract
The synthesis of copolymers from different feed ratios of N-(methacryloyloxymethyl) benzotriazole (MMBT) and glycidyl methacrylate (GMA)
was achieved by using free radical solution polymerization technique and characterized using FT-IR and 13 C NMR spectroscopy. The thermal
stability of the synthesized copolymers was studied using thermogravimetric analysis (TGA). The corrosion performances of mild steel specimens
dip coated with different composition of copolymers were investigated in 0.1 M HCl using potentiodynamic polarization and electrochemical
impedance spectroscopic (EIS) method. The polarization and impedance measurements showed different corrosion protection efficiency with
change in composition of the copolymers. It was found that the corrosion protection properties are owing to the barrier effect of the polymer layer
covered on the mild steel surfaces. However, it was observed that the copolymer obtained from 1:1 mole ratio of MMBT and GMA exhibited better
protection efficiency than other combinations.
© 2007 Published by Elsevier B.V.
Keywords: Methacrylic copolymers; N-(Methacryloyloxymethyl) benzotriazole; Corrosion protection; Impedance spectroscopy; Polarization
1. Introduction
Mild steel has been extensively used for many mechanical and
structural engineering purposes. Corrosion of mild steel has an
enormous economic impact. The understanding of the corrosion
problem and the solution to tackle this problem is a very active
field of research. Acid solutions (HCl and H2 SO4 ) are widely
used in industry and the most important areas of application are
industrial acid cleaning, acid pickling, acid descaling, oil well
acidising and other petrochemical processes. However, the main
problems in using mild steel in these applications are due to the
uniform corrosion attack. At this juncture, there is a need to
improve the corrosion performance of the mild steel. This can
be achieved by adding appropriate concentration of the organic
compounds as inhibitors.
The applicability of organic compounds as corrosion
inhibitors has been recognized for a long time [1–7]. The action
of inhibition of the corrosion of steel and iron in acidic media
∗
Corresponding author. Tel.: +91 44 2223 7276; fax: +91 44 2223 2403.
E-mail address: nrajendran@annauniv.edu (N. Rajendran).
0300-9440/$ – see front matter © 2007 Published by Elsevier B.V.
doi:10.1016/j.porgcoat.2007.08.001
by organic compounds containing heteroatom has been widely
studied [8–18]. In general, inhibitor compounds form a protective film on an oxidized mild steel surface [19]. Moreover,
nitrogen-containing heterocyclic compounds are considered to
be effective corrosion inhibitors [20–24]. Among these, benzotriazole has been proved to be one of the most important
inhibitors for corrosion inhibition of mild steel in acid medium
[24–32]. The effectiveness of benzotriazole has been related to
the chelating action of heterocyclic molecules and the formation
of a physical blocking barrier on the metal surface [33].
Recently, organic polymer coatings play an important role in
the protection of metals in many environments. However, much
less attention has so far been paid in the application of polymer
coatings for corrosion protection of mild steel from corrosion.
Coatings restrict interaction between anodic and cathodic sites
at the coating-metal interface partly by impeding penetration of
the electrolyte but, more importantly, by minimizing formation
of a bulk electrolyte phase at the coating-metal interface [34].
The mechanisms of corrosion protection by organic coatings
have been extensively discussed in the literature [35].
Of the various types of organic polymer coatings that are
in use, especially methacrylic polymers are considered as one
A.P. Srikanth et al. / Progress in Organic Coatings 60 (2007) 320–327
of the best organic coating materials today [36]. Its unique
properties like fast setting, high tolerance to contaminated surfaces and capable of making excellent bonding with metals, all
these have made it a candidate of great technological promise
[37,38]. Among all, they are used as binders in protective coatings because of their excellent durability [39]. Hence, there is
increasing interest in the use of methacrylic polymers as components of corrosion-resistant coating systems [40].
The focus of the present study was to exploit the adhesive behavior of methacrylates and the inhibiting behavior of
benzotriazole. Poly(N-methacryloyloxymethyl benzotriazoleco-glycidylmethacrylate) [poly(MMBT-co-GMA)] having different compositions were synthesized using different mole ratios
of N-methacryloyloxymethyl benzotriazole (MMBT) and glycidylmethacrylate (GMA) and dip coated on mild steel to
increase the adhesion and corrosion resistance. To evaluate the
corrosion protection properties of these copolymers, the electrochemical experiments such as potentiodynamic polarization and
electrochemical impedance spectroscopic (EIS) studies were
carried out with mild steel samples dip coated with different
compositions of the copolymers in 0.1 M HCl.
2. Experimental details
2.1. Materials
The mild steel samples embedded in a polymer setting had an
area of exposure of 1 cm2 . These specimens were mechanically
polished using different grades of emery paper. They were sub-
321
sequently washed with double distilled water, degreased with
methanol and then dried at room temperature. 0.1 M concentration of the acid was prepared from AR grade HCl using double
distilled water. Benzotriazole (SRL), triethyl amine (Aldrich),
formaldehyde (30% solution) were used as received without
purification. Ethyl methyl ketone was purified by dehydrating
with anhydrous K2 CO3 and then distilled. The GMA (Fluka)
was distilled under reduced pressure to remove the inhibitor and
stored in a refregirator. Benzoyl peroxide (BDH) was purified by
recrystallisation from 1:1 mixture of methanol and chloroform.
2.2. Synthesis of various compositions of
poly(MMBT-co-GMA)
Initially, N-hydroxymethyl benzotriazole was synthesized
according to a previously reported experimental procedure
[41]. In the second stage, N-methacryloyloxy methyl benzotriazole (MMBT) was synthesized by reacting N-hydroxymethyl
benzotriazole (8.68 g, 0.044 mol) with methacryloyl chloride
(4.8 g, 0.044 mol) in ethyl methyl ketone (EMK) (300 ml) in
the presence of triethylamine (4.4 g, 0.044 mol) maintained
in the temperature range of 0–10 ◦ C. In the third stage, the
copolymer, poly(MMBT-co-GMA) having different compositions were synthesized by free radical solution copolymerization
of the monomers MMBT and GMA at different mole ratios
using benzoyl peroxide (BPO) as initiator in EMK solvent.
A schematic representation of the synthesis of MMBT and
poly(MMBT-co-GMA) is shown in Scheme 1.
Scheme 1. Synthesis of poly(MMBT-co-GMA).
ID
693718
Title
Synthesis,characterizationandcorrosionprotectionpropertiesofpoly(N-(methacryloyloxymethyl)
benzotriazole-co-glycidylmethacrylate)coatingsonmildsteel
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