Related studies to cathodic protection of reinforced concrete structures (FHWA-OK-83-06)

Cathodic protection of steel in portland cement concrete requires information concerning several different areas. This report describes studies which were pointed toward developing an understanding of several of these. A study of making an asphaltic concrete conductive was accomplished using coke breeze mixed with asphalt and aggregate. Mixes containing 45% coke breeze, 7-11% asphalt and the remainder a standard aggregate were found to be appropriate for conductive layers for cathodic protection. It was found possible to determine corrosion rates electrochemically using linear polarization. This laboratory technique gave corrosion rates similar to values obtained in other laboratories using other techniques. Testing in the laboratory and bridge decks of molybdneum-molybdneum oxide electrodes indicated these would be useful as embeddable reference electrodes in concrete. Silver-silver chloride electrodes were not found to be stable in this application. These electrochemical half-cells, Mo/MoO should prove to be useful for cathodic protection systems which require controlled potentials. Reinforced concrete cylinders were exposed to cathodic protection level currents for five years. Pullout strengths and concentrations of sodium, potassium and chloride ions were determined throughout this time period. These data indicate the cathodic protection currents reduce the bond strength of the steel and concrete after about 3.5 years, due to accumulation of sodium and potassium at the interface between steel and concrete.Final ReportN

Addition of IrO2 to RuO2+TiO2 coated anodes and its effect on electrochemical performance of anodes in acid media

AbstractTernary mixed metal oxide coatings with the nominal composition IrxRu(0.6−x)Ti0.4O2 (x=0, 0.1, 0.2, 0.3) on the titanium substrate were prepared by thermal decomposition of a chloride precursor mixture. Surface morphology and microstructure of the coatings were investigated by Scanning electron microscopy (SEM), Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. Systematic study of electrochemical properties of these coatings was performed by cyclic voltammetry (CV) and polarization measurements. The corrosion behavior of the coatings was evaluated under accelerated conditions (j=2Acm−2) in acidic electrolyte. The role of iridium oxide admixture in the change of electrocatalytic activity and stability of Ru0.6Ti0.4O2 coating was discussed. Small addition of IrO2 can improve the stability of the RuO2+TiO2 mixed oxide, while the electrocatalytic activity for oxygen evolution reaction (OER) is decreased. The shift of redox potentials for Ru0.6Ti0.4O2 electrode that is slightly activated with IrO2 and improvement in the stability can be attributed to the synergetic effect of mixed oxide formation

Related studies to cathodic protection of reinforced concrete structures - final report (FHWA-OK-82-06)

Cathodic protection of steel in portland cement concrete requires information concerning several different areas. This report describes studies which were pointed toward developing an understanding of several of these. A study of making an asphaltic concrete conductive was accomplished using coke breeze mixed with asphalt and aggregate. Mixes containing 45% coke breeze, 7-11% asphalt and the remainder a standard aggregate were found to be appropriate for conductive layers for cathodic protection. It was found possible to determine corrosion rates electrochemically using linear polarization. This laboratory technique gave corrosion rates similar to values obtained in other laboratories using other techniques. Testing in the laboratory and bridge decks of molybdneum-molybdneum oxide electrodes indicated these would be useful as embeddable reference electrodes in concrete. Silver-silver chloride electrodes were not found to be stable in this application. These electrochemical half-cells, Mo /MoO should prove to be useful for cathodic protection systems which require controlled potentials. Reinforced concrete cylinders were exposed to cathodic protection level currents for five years. Pullout strengths and concentrations of sodium, potassium and chloride ions were determined throughout this time period. These data indicate the cathodic protection currents reduce the bond strength of the steel and concrete after about 3.5 years, due to accumulation of sodium and potassium at the interface between steel and concrete.Final ReportN