G. Batis

CORROSION PROTECTION INVESTIGATION OF REINFORCEMENT BY INORGANIC COATING IN THE PRESENCE OF ALKANOLAMINE-BASED INHIBITOR

Corrosion of reinforced concrete structures is a major problem throughout the world, demanding significant amounts for repair and rehabilitation. Corrosion protection is commonly performed by coating the concrete or by using corrosion inhibitors. This paper describes the comparative evaluation of the effectiveness of an acrylic dispersion and an inorganic coating on silicate basis, of an alkanolamine-based corrosion inhibitor and of their combination, on reinforced mortar specimens partially immersed in 3.5% NaCl solution. The following techniques were used: strain gauges, measurements of the corrosion potential, the mass loss and the EIS of the reinforcing bars and measurements of the chloride diffusion and the carbonation depth in mortars. Results demonstrate that the simultaneous use of the alkanolamine-based corrosion inhibitor with the inorganic coating offers a protection degree comparable to that of the acrylic dispersion, which performs best in the presence of both chloride ions and carbon dioxide.

Study of the effect of AC‐interference on the cathodic protection of a gas pipeline

The aim of this fieldwork was the study of the effect of 50Hz AC, induced by high‐voltage power lines, on the cathodic protection system of a natural gas pipeline. The effectiveness of cathodic protection was checked through in situ long‐term monitoring and analysis of pipeline electrical parameters. The results gave an insight into the problems of the cathodic protection system operation, caused by AC interference. An AC and DC potential interdependence was observed, that previously has hardly been reported, and was scrutinized in relation to cathodically protected pipelines. The effects of the AC‐interference and low frequency DC potential fluctuations, as well as the potential deviations from the protection potential, are examined. These phenomena are associated with corrosion susceptibility and difficulties in obtaining reliable cathodic protection measurements.

Simulation of cathodically protected pipeline with capacitive AC mitigation devices for interpretation of misleading instant Eoff readings

Abstract A cathodically protected buried pipeline is usually connected to earthing electrodes via several capacitive AC mitigation devices placed at various locations along the pipeline in order to decrease the AC voltage interference. During periodic switching of the cathodic protection circuit for the instant Eoff measurements, the capacitive AC mitigation devices tend to be discharged through the soil provoking an error in the instant Eoff readings, thus resulting to a possible false evaluation of the cathodic protection effectiveness. The aim of the present work is to investigate the role of the main factors, which influence this error. An electric circuit simulation of the pipeline with connected earthed capacitors is proposed. The circuit analysis has shown that the key determining factors of the aforementioned capacitive discharge time constant comprise the capacitance value of the capacitive AC mitigation device at every earthing site, the number of earthing sites where the capacitive AC mitigation devices are installed, the earthing electrodes resistance and the pipeline (or coating) resistance to remote earth. Measures to minimise this misleading error of Eoff readings through the control of the abovementioned factors and the modification of the time of the Eoff measurement are suggested. In this context, the Eoff should be measured at prolonged time after every switching, contrary to the usual practice. Furthermore, the capacitive AC mitigation devices should not be disconnected from the pipeline in order to prevent the adverse effects of AC interference on cathodic protection monitoring. The present work contributes to the understanding of the capacitive AC mitigation devices effect on pipeline cathodic protection monitoring, which has been rarely analysed in the past. Moreover, by recommending novel approaches, the paper can stand as a reference to the cathodic protection operators for a simple, reliable and economic monitoring of the cathodic protection effectiveness in presence of earthed capacitive AC mitigation devices.

Evaluation of parameters influencing reinforcement corrosion by means of a strain gauge technique

A number of applications selected with variations of factors affecting the corrosion of mortar steel reinforcements are discussed in this paper. Corrosion estimation by means of a strain gauge (SG) technique was used in several cases to confirm the validity of the method. The efficiency of corrosion inhibitors, the protection offered by the addition of minerals, the curing time influence, and the corrosion resistance of various steel types can be estimated by means of the short term SG test technique. Good correlations were found in all cases of application between the corrosion rates computed from SG technique and the mass loss data. Additionally, the method was applied for swelling measurements of mortar specimens caused by the degradation of FRP reinforcements in the corrosive environments.

Dechlorination of large marine iron artifact using a novel technique involving impressed current

Purpose – This paper aims to develop an electrochemical dechlorination method for large objects in a short time, which were for a long time in the sea. Traditionally, in conservation, chlorides are extracted from marine iron artifacts using complete immersion of those objects in alkaline solutions with or without electrolysis. However, these techniques are time-consuming and very costly, especially when applied to large marine artifacts such as cannons and anchors. Design/methodology/approach – An appropriate sponge was chosen based on resistance to NaOH and the rate of exacted chlorides. Application of electrochemical dechlorination in situ and removal of chloride were measured by the scanning electron microscope (SEM)-EDAX method on the corrosion products and by titration of the electrolysis solution. X-ray diffraction (XRD) method is used for identification of corrosion products before and after application of electrochemical chloride extraction. Findings – The electrochemical chloride extraction (ECE)...