Influence of electrosynthesis potential on corrosion performance of polypyrrole coated stainless steel and its mechanism research

Abstract

The electrosynthesis process of conducting polymer on stainless steel was investigated and a two-step process was adopted to obtain polypyrrole (PPy) films at low potentials. The effects of applied potentials on the electrochemical, structural and protective properties of PPy films have been explored using scanning electron microscopy, infrared spectroscopy, cyclic voltammetry, open circuit potential and potentiodynamic polarisation. Films electrodeposited at lower potentials have more homogeneous morphology and less overoxidation. The electroactivities decrease as applied potentials increase. Polypyrrole films exhibit effective inhibition of corrosion for stainless steel in 3?5%NaCl solution. Applying lower potential for the synthesis improves the anticorrosive efficiency of PPy film. The anodic current during polarisation process for stainless steel/PPy is mainly ascribed to the dissolution of stainless steel at pinhole defects for initial immersion, and to PPy oxidation after short time immersion.

Cyclic Voltammetric Synthesis of Poly(N-methyl pyrrole) on Copper and Effects of Polymerization Parameters on Corrosion Performance

“…Using this initial potential, the optimum upper potential limit was examined by electrodepositing PNMPy at various upper potential limits (+0.9 and +1.0 V) while keeping the scan rate (20 mV/s) and cycle numbers (20 cycles) fixed. Meanwhile, it was reported that polymer films will be irreversibly overoxidized at high potentials resulting in loss of conductivity and electroactivity as well as degradation of mechanical properties. , The overoxidation of polymer film also leads to an increase in its permeability, thus the coating becomes less protective and the applied potential is also expected to affect the corrosion performance of the polymer film. In order to prevent further oxidation of the polymer film, Tüken et al limited the upper potential at +0.85 V during the cyclic voltammetric synthesis of PNMPy on a mild steel electrode in 0.3 M oxalic acid medium .…”

“…As immersion goes on, PNMPy film will loose its electroactivity, thus the ability to reduce and oxidize successively and reversibly, vanishes. The successive and reversible conversion of doped form to undoped form may induce fatigue-like stress that could be responsible for cracking …”

“…The successive and reversible conversion of doped form to undoped form may induce fatigue-like stress that could be responsible for cracking. 48 In order to further reveal the corrosion protection ability of PNMPy coating, anodic polarization curves were recorded for Cu and Cu/PNMPy electrodes in 0.1 M H 2 SO 4 solution, and the polarization curves were shown in Figure 10. The selection of a 168 h period to perform anodic polarization scan for Cu/ PNMPy is related with the best corrosion performance of the polymer film, and this period was determined from the impedance measurements.…”

“…Poly(pyrrole) is a potential material among conducting polymers, due to its high conductivity, stability, relatively ease of synthesis, and eco-friendly features. , There have been many studies on the investigation of poly(pyrrole) as an anticorrosive coating for the protection of various metals, such as magnesium, iron, aluminum, steel, , and copper, ,,,− and it was demonstrated that the poly(pyrrole) enhances the resistance of these metals against corrosion in different aggressive media. In contrast to the works related with the corrosion protection properties of poly(pyrrole), little attention has been paid to the study of pyrrole derivatives.…”

Facile synthesis of highly conductive PPy/graphene nanosheet /Gd3+ composites

“…The electrically conducting polymers such as polypyrrole (PPy) are particularly promising owing to their highly electrical conductivity, corrosion performance, ease of low cost synthesis and environmental stability. 13,14 However, the disadvantages of PPy can not be ignored, such as not easily soluble in common organic solvents, processing difficulties and relatively low conductivity, which has limited the application of PPy in practice. 15 In order to improve the properties of PPy, a series of conducting PPy composites were prepared by using graphite/graphene as the conducting filler to explore their potential applications as high-performance materials.…”