| Engine power density becomes higher and higher. The popularity of the aluminum alloy application is growing. People’s environmental protection consciousness is increasing. Therefore, the traditional engine coolant is being challenged with more and more severe problems come out. However, inorganic coolants are used commonly in domestic industry. Inorganic coolants contain substances which are eliminated or will be eliminated in abroad, such as boric acid salt, nitrite, molybdate salt etc. It is demonstrated that the advantages of organic coolant include high performance in applications, comprehensive protection effect, low consumption, and environmental safety. It is a general tendency that organic coolant(OAT) will take the place of inorganic coolant. Therefore, preparation of efficient low-cost environment-friendly engine coolant inhibitors for development is valuable in the economic and social benefits.In this paper, the performance of more than 20 organic acid inhibitors was tested. Then the aliphatic acid and dibasic acid was compounded, combined with other coolant additives. Its corrosion performance was evaluated under the conditions of laboratory test. The research contents and the results are summarized as follows:1) The electrochemical polarization method was applied to study the inhibiting performance of more than 20 corrosion inhibitors with water- ethylene glycol system as medium. Effective inhibitors for copper, brass, carbon steel, cast iron, cast aluminum and solder were chosen. The results showed that benzene triazole was a special corrosion inhibitor for copper. Sodium benzoate showed the best protection for steel. Octylic acid, sebacic acid and methyl benzene also showed reasonable protection for steel. Isocaprylic acid was the best inhibitor for iron. Sodium benzoate exhibited significant protection for solder. Cast aluminum was difficult to protect. Heptylic acid was the only inhibitor effective for cast aluminum. In a word, a single corrosion inhibitor is difficult to achieve corrosion protection for a variety of metals.2) Electrochemical polarization method was also adopted to study the inhibiting performance of benzoic/sebacic and isocaprylic/sebacic compounded inhibitors with water- ethylene glycol system as medium. The influence of pH, the percent of benzoate and isocaprylic, the mole ratio of benzoic/sebacic and isocaprylic/sebacic, the BTA content, along with other additives on the performance of the compounded inhibitors was investigated. The results showed that the compounded inhibitors had the best synergistic effect when benzoic content is 0.6wt% and the mole ratio of benzoic/sebacic is 5.9. Six metals could be protected simultaneously. The protection performance would be reduced when the content of benzoicis was too high or too low, or when the mole ratio of benzoic and sebacic was too large or too small. Benzene triazole had better effect than toluene triazole in this system. However, simultaneous protection for the six metals by using isocaprylic/sebacic compounded inhibitor at one certain mole ratio of isocaprylic and sebacic. There are some other effective additives for aluminum such as methyltert-butylether, diethylene glycol methyl ether, p-hydroxy benzoic ether, and glycerol.3) The inhibiting performance of ethylene glycol base engine coolant(#25) was studied by electrochemical polarization method and glassware corrosion weight-loss method with benzoic/sebacic/ Benzene triazole as compounded inhibitor. Some other additives had been also added. The influence of inhibitor content, dye and defoamer on the inhibiting performance of the coolant was also investigated. Finally, the formula had been optimized. This formula showed good corrosion inhibition, long life, storage stability, hard water resistance, good environmental protection, and cheapness. Such properties are comparable to that of the American products. |
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