Certain Anti-Wear (AW) and Extreme Pressure (EP) lubricant additives are corrosive to yellow metals. The Copper Strip Corrosion test qualifies the corrosively of an oil to a polished copper strip. The polished copper strip is coated with the lubricant in question and placed in a heated water bath for 3 hours. The tarnish color of the copper strip is then compared to ASTM standards and given a rating. Quality lubricants will have a rating of 1A or 1B. Generally, the rating should be less than 3 for a ‘pass’ rating.
The Copper Strip Corrosion test should not be a part of your routine analysis program. It is a quality check of the lubricant and should be performed for evaluation of new oils or when tarnishing or corrosion of yellow metals are suspected or apparent.