Corrosion protection study of polypyrrole/PW12O403- coatings on carbonsteel electrodes embedded in cement mortars

摘要

Hybrid polypyrrole/PW12O40 3- (PP) films were electrochemically synthesised on carbonrnsteel (CS) electrodes in acetonitrile medium. Both, potentiostatic and potentiodynamicrnmethods were used in 0.2 M pyrrole and 0.01 M H3PW12O40 solutions. Since CS electrodesrndissolve under these working conditions, a passive layer was necessary to create on thernelectrodes by potentiodynamic polarisation in 0.1 M LiClO4 + CH3CN prior the PPrnelectrosynthesis. To improve the corrosion resistance, the polymer just electrosynthesised wasrnreduced (PPR) by cyclic voltammetry in 0.1 M LiClO4 + CH3CN.rnA comparative study of corrosion current density (icorr) measurements (using thernPolarisation Resistance technique) was carried out with CS electrodes in bare condition andrncovered by PP and PPR. Measurements were taken in two types of different solutions: byrnfiltering Portland cement (PC) and by calcium aluminate cement (CAC) water mixtures, withrn0.15 M NaCl as corroding agent. Also, the concentrations of Fe ions were determined by thernstandard method ISO 6685-1982. PPR covered electrodes showed better properties againstrncorrosion than PP covered and CS bare electrodes in PC water mixtures. Also, the Fe ionrnconcentration was considerably lower in PPR electrodes than in CS electrodes.rnEcorr, icorr and gravimetric loss measurements, among others, were carried out on PPrnelectrodes embedded in PC and CAC mortars, and the response compared to the one for barernCS electrodes. Two types of aggressive media were used: on one hand the mortars wererndipped in seawater, and on the other hand they were submitted to an accelerated carbonationrnprocess in CO2-saturated atmosphere. PP covered electrodes embedded in CAC mortars didrnnot present good properties against corrosion in seawater media. In contrast, PP coveredrnelectrodes embedded in PC mortars dipped in seawater showed good protection againstrncorrosion. Bare CS and PP covered electrodes embedded in CAC mortars were both protectedrnagainst corrosion after the carbonation process. Polymer coatings showed a slightly betterrnbehaviour against corrosion in PC mortars submitted to an accelerated carbonation process inrncomparison with bare CS electrodes.