Evaluation of Oil Corrosiveness
Office of Automotive Engineering



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image of metal coupons, which are immersed in engine oil then examined for corrosion

Metal coupons are immersed in engine oil then examined for corrosion.


image of corrosion bench test (HTCBT) procedure

Four metal coupons, copper, lead, tin, and phosphor bronze, are used in the high-temperature corrosion bench test (HTCBT) procedure.

The standard test methods for evaluating the corrosiveness of diesel engine oil, ASTM D6594 and ASTM D5968, are bench tests that evaluate diesel engine lubricants to determine their tendency to corrode alloys of lead and copper.

Some oils may inadequately inhibit the chemical attack of non-ferrous metals commonly used in bushings, bearings, cam followers, and oil coolers in diesel engines.

ASTM D6594 evaluates these corrosive tendencies at the higher temperatures (135°C) found in some engines, and ASTM D5968 uses an alternate test temperature (121°C). These test methods have been found to correlate with an extensive fleet database containing corrosion-induced cam and bearing failures.

HTCBT Procedure

The high-temperature corrosion bench test (HTCBT) procedure is conducted by immersing four metal coupons including copper, lead, tin and phosphor bronze in a measured amount of engine oil. Air is passed through the oil at an elevated temperature for a period of time. When the test is completed, the coupons and stressed oil are examined to detect corrosion. Concentrations of copper, lead and tin must be below defined levels to meet individual specification requirements.

Related Terminology

diesel engine lubricants  •  oil corrosiveness  •  bench test  •  evaluation of corrosiveness  •  diesel engine oil  •  ASTM D6594  •  ASTM D5968  •  HTCBT/CBT

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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 10 technical divisions.
05/14/14