Inhibitive properties of sodium gluconate and biocide (CTAB) on corrosion, biocorrosion and scaling controls of copper in cooling water systems

摘要

The use of water as thermal fluid in cooling circuits usually leads to three phenomena namely: Corrosion, scaling and biological fouling, which constitute the cause of a decrease in thermal and electrical efficiency of water circuits, a loss of metallic material and the proliferation of microorganisms in the water circuits. In this study, the characterization of the studied water was effectuated and has revealed that it is corrosive, scaly and seat of development of the microorganisms. Then researches of new formulations have been started in order to propose effective solutions for protection of cooling circuits. First of all, our choice was made on sodium gluconate (GS), combined with cetyltrimethyl ammonium bromide biocide (CTAB) used to fight against the proliferation of microorganisms. The investigation of obtained results by using electrochemical methods has demonstrated that GS is an efficient corrosion and scaling inhibitor with efficiency close to 95% at 10~(-3)M. Also the study has shown that CTAB biocide is a mixed type inhibitor with a good inhibitory efficiency of 86% at 15 ppm. In addition, the optimization of GS and CTAB concentrations was carried out by an electrochemical study in order to find a formulation to prevent cooling circuits from the problems previously mentioned. The formulation found (10~(-3)M of SG + 15 ppm of CTAB) has a better performance and has an efficiency of the order of 89% which improves with the immersion time to reach 94% after 24 hours and it keeps its performance with higher temperatures. The Scanning Electron Microscopy (SEM, Energy dispersive X-ray (EDX) and X-ray Diffraction (XRD) analysis have shown that this formulation is an efficient inhibitor for corrosion, scaling and biological fouling. These analyses confirm all results obtained by potentiodynamic polarization curves and electrochemical impedances spectroscopy.