Corrsion Of Typical Metals In Ethylene Glycol-Water-based Cooling Liquid

Coolant plays a very important and indispensable role in electronic equipment liquid cooling system with a high-power and a high-heat-density.It is significant to study the corrosion behavior of typical metal materials in the coolant and to establish the operations guide for controlling the quality and performance in the complex cooling liquid system.In this paper,the effects of temperature,pH and impurity ions(Cl-,Fe3+,Cu2+)on the corrosion of cast aluminum,antirust aluminum,carbon steel and brass were studied firstly.And then,the synergistic effects between the pH values of the coolant and the additions of impurity ions on the corrosion behavior of these four kinds of metals were further studied.Finally,the electrochemical mechanism of typical metals in the coolant was investigated by electrochemical technique.The results showed that:the corrosion rate of cast aluminum,antirust aluminum,carbon steel and brass increased with the coolant temperature.The corrosion of carbon steel was the most serious,and its corrosion rate was the highest in the coolant at 90?.The corrosion rate of cast aluminum,antirust aluminum and brass changed a little with decreasing the pH of the coolant.However,there was an obvious effect of pH values on carbon steel.When the Cl-concentration increased in the coolant,the corrosion rate of cast aluminum and antirust aluminum increased.Comparatively,the corrosion rate of carbon steel was higher.Fe3+ and Cu2+ concentration in the coolant,had little effects on the corrosion rate of these four kinds of metals.Therefore,under normal operations,the pH of the coolant should be lower than 7.5,and Cl-,Fe3+,Cu2+concentrations should below 10 ppm.It was found that pH values,Cl-,Fe3+ and Cu2+ concentrations of the coolant,had synergistic effect.These synergistic effects had a greatest effect on the corrosion of brass.What's more,two factors of Fe3+/Cl-and three factors of Fe3+/pH/Cl-had the greatest synergistic effect on the corrosion of these four kinds of metals.The corrosion process of brass in the coolant was controlled by anodic and cathodic mixing process.The corrosion process of cast aluminum and antirust aluminum carbon steel in the coolant were controlled by the anodic passivation.The increment of concentrations of the coolant didn't influence the corrosion process of these four kinds of metals.However,when Cl'concentration in the coolant increased,the corrosion process of cast aluminum and antirust aluminum will gradually be changed from the anodic passivation process control to anodic and cathodic mixing process control.EIS characteristics of cast aluminum,antirust aluminum in the coolant,were composed of the resistance of a deformed capacitive loop the the high frequency area and low frequency area,with two time constants.EIS spectras of carbon steel and brass were composed of a capacitive loop in the high frequency area and a Warburg impedance in the low frequency area.Whether the single factor of pH,Cl-,Fe3+ and Cu2+,or synergistic effects of two factors,three factors and four factors,the cast aluminum,antirust aluminum,carbon steel and brass didn't influence the characteristics of EIS spectra.