Solar Aluminum Heat Exchanger Inhibitor Studies

Pipelines of solar cycle system are made of a variety of metals; the most common materials are carbon steel and aluminum alloy. Solar heat exchanger of aluminum alloy connects to the connecting pipe and the collector to form a closed system, because of the heat exchanger with antifreeze, corrosion of heat exchangers and other pipelines are easily caused by long-term work so as to decrease the service life of the water heater.In order to avoid material corrosion caused by long-term work in antifreeze, corrosion inhibitors should be added in antifreeze to prevent the corrosion. Therefore, corrosion inhibitor technology is used in the solar heat exchanger of aluminum alloy in this paper to improve the corrosion resistance of heat exchanger, so as to give longer life of heat exchanger, ensure the normal and safe use of the solar water heater, and reduce the economic losses caused by the broken of the heat exchanger. Corrosion inhibitors of aluminum alloy are widely studied and used in simulate seawater environment in this paper, which has an important significance to ensure and improve the service life of the heat exchanger in the solar system.In this paper, more than forty compounds are theoretically chosen and their inhibiting effects on corrosion of7075aluminum alloy in3.5%NaCl solution are evaluated by weight-loss method, electrochemical polarizations and scanning electron microscopy technology. Then some kinds of compounds with excellent corrosion inhibition effect have been got in3.5%NaCl solution. A composite and excellent corrosion inhibitor is developed by orthogonal method. Experimental results show that heterocyclic compounds containing sulfhydryl (2-mercaptobenzothiazole,2-mercaptobenzoxazole and2-mercaptobenzimidazole) have no inhibition effect on7075aluminum alloy, and heterocyclic compounds containing nitrogen have certain inhibition effect on7075aluminum alloy. The effect of composite corrosion inhibitor is better than the inhibitor of single component. Barbituric acid and Tween80have good corrosion inhibition when they are used alone, but they have no inhibition effect on aluminum alloy when they are added in composite corrosion inhibitor. Cerium chloride has no obvious inhibition effect on aluminum alloy when it is used alone, but it has good corrosion inhibition as an additive in composite corrosion inhibitor. Therefore, the effect of composite corrosion inhibitor is best when the concentration of the three compounds of1H-Benzotriazole,2-aminopyridine and cerium chloride were1.5,0.1, and0.5g/L in this experiment.Due to corrosion inhibitors exist in the practical application of narrow applicable scope, poor solubility in water and unfriendly to the environment, corrosion inhibitor should be developed which has good corrosion inhibition effect for both aluminum and iron.So iron samples and aluminum samples are chosen according to the condition of equipment, the composite corrosion inhibitor is developed by a lot of experiments based on the research of aluminum corrosion inhibitors. The inhibiting effects of more than thirty compounds on corrosion of7075aluminum alloy in3.5%NaCl solution are evaluated by weight-loss method, orthogonal experiment method and scanning electron microscopy technology. Scanning electronic microscopy (SEM) is used to examine the surface morphology of corrosion samples. Experimental results show that CeCl3has good inhibition effect on aluminum but aggravate the corrosion of iron. Sodium Polyacrylate can make aluminum corrosion uniformity when it is used alone, but it can increase the weight loss of aluminum. Good synergistic effect may be generated among1H-Benzotriazole,3,5-Diamino-1,2,4-triazole, Cinnamaldehyde, Tween80and Polyvinylpyrrolidone. They have good corrosion inhibition effect for both aluminum samples and iron samples. Therefore, the composite corrosion inhibitor have best inhibition effect when the concentration of the five compounds of1H-Benzotriazole,3,5-Diamino-1,2,4-triazole, Cinnamaldehyde, Tween80and Polyvinylpyrrolidone were1.0-1.5g/L,0.05～0.1g/L,0.1g/L,0.5～1.0mL/L and1.0～1.5mL/L in this experiment.