ASTM D1384 Serves as Model for Testers

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Cavitation pittin

Samples were tested for corrosion protection following the ASTM D1384 Corrosion in Glassware method (www.astm.org). Samples were diluted to 33-percent glycol, dosed with ASTM synthetic corrosive water (similar to 2-percent seawater), continuously aerated, and heated to 190 degrees for two weeks. As a laboratory control, a reference coolant (ASTM D 3585) was also exposed to provide a baseline.

At the end of the test period, the samples were cleaned according to a specified ASTM procedure, dried, and evaluated for both a change in appearance and loss in weight. While this is not considered to be a definitive test of acceptability-extensive fleet testing is always the bottom line-it has a long history as a screening test. Because the test is run with synthetic corrosive water and because of the accelerated nature of the testing, it is best not to read too much into minor differences between products, so long as they meet ASTM specification.

All of the tested engine coolants performed well in the screening level test-literally 1,000 times better than raw water-but there were some differences in performance. Winterization products (-50 burst-point propylene glycol formulas) performed surprisingly well for products intended for much milder conditions; however, we do not recommend any winterization product for engine coolant service-and neither do their respective manufacturers.

Diesel coolants were tested for cavitation pitting by exposing cast-iron coupons in an ultrasound bath for four hours, simulating cylinder-liner ringing. Any evidence of pitting or freckling was considered to be a failure. The purpose of this test was to identify coolants that effectively combat cylinder liner pitting.

The very best coupons, not surprisingly, were from the heavy-duty coolants, specifically formulated to endure the sort of torture commonplace in a heavily loaded diesel engine. Though you might get away with any of the long-life coolants in diesel service, we still like the idea of using heavy-duty coolants in wet-sleeve diesels and in boat engines with severe duty cycles (commercial fishing boats, trawlers, anyone that runs long and hard).

We also tested the products freeze points; all concentrated coolants were properly diluted, and all concentrates met concentrate specifications.

Practical Sailor has been independently testing and reporting on marine products for serious sailors for more than 45 years. Supported entirely by subscribers, Practical Sailor accepts no advertising or any form of compensation from manufacturers whose products we test. Testing is carried out by a team of experts from a wide range of fields including marine electronics, marine safety, marine surveying, sailboat rigging, sailmaking, engineering, ocean sailing, sailboat racing, and sailboat construction and design. This diversity of expertise allows us to carry out in-depth, objective evaluation of virtually every product available to serious sailors. Practical Sailor is edited by Darrell Nicholson, a long-time liveaboard sailor and trans-Pacific cruiser with more than three decades of experience as a marine writer, photographer, boat captain, and product tester. Before taking on the editor’s position at Practical Sailor, Darrell was the editor of Offshore magazine, a boating-lifestyle magazine serving the New England area. Darrell has won multiple awards from Boating Writer’s International, including the Monk Farnham award for editorial excellence. He holds a U.S. Coast Guard 100-ton Master license and has worked as a harbor pilot and skippered a variety of commercial charter boats.

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