Volume 4, Issue 1 (January 2007)
New Electrochemical Methods for the Evaluation of Localized Corrosion in Engine Coolants
Due to the need of increasing energy efficiency, reducing pollution and lessening dependency on petroleum, vehicles using more advanced propulsion technologies such as fuel cell and hybrid electric (e.g., gasoline-electric or diesel-electric hybrid) power are being developed constantly. At the same time, extensive development efforts are being devoted to research aiming to increase the use of lighter metals such as magnesium alloys in today's engines. New engine coolants are often required to meet many of these new developments and the associated changes in cooling system requirements. Since corrosion protection is one of the key performance parameters for engine coolants, new and more effective corrosion measurement methods are useful for evaluating old and developing new coolants to meet the needs of new cooling systems or having improved corrosion protection performance, or both. Particularly, new electrochemical methods capable of more reliable, quantitative, and fast (ideally, real-time) measurements of localized corrosion such as pitting, crevice, and under-deposit corrosion, and corrosion under heat rejecting conditions are highly desired. Existing ASTM test methods for engine coolants either rely on inspection of the sample after a relatively long exposure period to determine the extent of localized attack or do not yield results directly related to localized corrosion. In this paper, coupled multi-electrode sensors test and simulated localized corrosion cell technique are compared and discussed to gain new insight for facilitating the development of more effective inhibited coolants.