SEDL / STP / STP887-EB / STP32985S

Observations on Aluminum Water Pump Cavitation Tests

Oakes, BD
corrosion inhibitor consultant, Welchem, Inc., Houston, TX

Pages: 18    Published: Jan 1986

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Abstract

Two water pump cavitation tests are currently used by automotive coolant suppliers that wish to sell coolants to automobile manufacturers in the United States. One test is ASTM Test for Cavitation Erosion-Corrosion Characteristics of Aluminum Pumps with Engine Coolants (D 2809). The other is Ford Laboratory Test for Cavitation Erosion-Corrosion Characteristics of Engine Coolants on Aluminum Coolant Pumps (BL 3-1). Details of the test methods are given in the respective ASTM and Ford publications.

Phosphate is confirmed to have a beneficial effect on cavitation. Silicate is shown to be beneficial when used with borate or benzoate, but it can be detrimental to the performance of phosphate. Materials of construction in the test apparatus, copper primarily, can affect the results obtained in the longer term Ford test. Coolants not particularly subject to cavitation appear to fail the test if copper from the test rig piping deposits inside the water pump. Cavitation is not observed with these coolants in the absence of copper. Coolants truly subject to cavitation will show it regardless of the construction materials in the test rig. Finally, it is observed that coolants that will not pass the ASTM pump test at the specified 1:5 concentration will often do so at a 1:2 concentration.