Abstract
The variation of coolants used in a multi-metal engine cooling system offers a challenge for corrosion inhibition. The diverse characteristics of this system are discussed along with their relationship to the selection of laboratory test methods to investigate inhibition.
A rotating specimen type of test is used for the evaluation. The effectiveness of inhibitors, such as sodium borate, sodium nitrite, sodium benzoate, potassium dichromate, soluble oil, and sodium mercap-tobenzothiazole, is compared by means of this test. Various test media are used, including ethylenegly-col-water mixtures and tap water with and without additional corrosive constituents. The metals investigated are steel, copper, brass, aluminum, cast iron and solder. The results are based on corrosion rate, microscopic examination, pit depth when applicable, and other general examinations.
This work includes the results of one year static room temperature tests on thirteen galvanic couple combinations for each inhibitor.
Based on the results obtained by conventional corrosion tests, a final examination of a combination of inhibitors is made in a laboratory model which simulates an engine cooling system. This test indicates effective inhibition by this combination in a system using either a copper-brass or aluminum radiator. 4.6.4
