Synthesis and Characterization of PANI/SBR Composites as Corrosion Protection Coating for Carbon Steel Substrates

Corrosion represents the main cause of deterioration in many widely used materials, such as carbon steel AC-1018. This damage costs millions of dollars every year and has yield to the development of corrosion protection science and technology.

Many commercial corrosion protection systems consist of coatings involving high toxicity and environmental risks, containing chromium, lead or cadmium, for example which are extremely harmful to human health. This situation has led to the arising of new materials capable of providing both sustainability and good enough corrosion prevention to compete with current systems.

Conducting polymers represent a promising alternative to achieve effective corrosion inhibition on carbon steel. Previous studies have demonstrated that conducting polymers induce steel to a passive state without environmental or health hazards. However, these polymers possess poor mechanical properties and low adherence to steel substrates, disadvantages which limit their practical application.

It has been demonstrated that it is possible to increase the stability and processability of conducting polymers by incorporating an elastomer, without significant diminishing of their desirable properties. Since the 90’s decade, several investigations have made inroads into the field of conducting polymer/elastomer composites by combining polyaniline (PAni) with different elastomers – such as nitrile rubber (NBR), ethylene-propylene-diene rubber (EPDM), styrene-butadiane-styrene rubber (SBS) and styrene-ethylene/butadiane-styrene rubber (SEBS) – following chemical, electrochemical and mechanical procedures. These materials were developed to be used as semiconducting elastomeric composites for a wide variety of applications but just a few of them have been proposed as anticorrosive coatings and hardly ever have their anticorrosive performance been tested in the literature.

Prior research works have also shown that the properties of this kind of materials are closely related to composition and dispersion of their constituents and that it is possible to raise PAni’s affinity with SBR by doping with dodecylbenzene sulphonic acid (DBSA) in order to attach a large substituent to the PAni’s molecule which increases its solubility in organic solvents.

Unlike some existing studies, which follow the electrochemical approach to obtain conducting polymer/elastomer composite materials, this study comprises the chemical synthesis of PAni by monomer oxidation and its further mixing with styrene butadiene rubber (SBR) elastomer by solution casting method to obtain a paint-like product which can be brushed over carbon steel. This work presents the electrochemical characterization of PAni-/SBR and PAni-DBSA/SBR films deposited on carbon steel substrates by cyclic voltammetry and polarization techniques to simulate material’s weathering and assess the effect of PAni/SBR composition and the use of DBSA as doping agent on their anticorrosive performance.