yellow erosion

[Kestas]

For the really curious, couldn't each person check for themselves if a lubricant attacks yellow metal? I don't know the particular ASTM spec number, but my STLE colleague regularly checks lubricants for how safe they are with yellow metals for our company, which manufactures bearings.

He simply puts a dab of lubricant on freshly cleaned copper strips and heats it to a certain temperature (150°F?) for a prescribed amount of time (less than a day?). He then compares the metal color against a chart. I expect a reactive lubricant would darken the copper rather quickly. Doing this test would give a more definite and irrefutable answer than spinning our wheels over any possible misinformation on any particular lubricant.

 

[bruce381]

ASTM D-130
Kinda forgot but think copper strip is heated in the Test Oil for 3 hours at 150F or maybe 210F.

Just do this take a couple inches of heavy copper wire like 12 gauge cut/pull off the plastic cover dunk it into a sample of oil half in half out set for 24 hours.

Pull out wire and compare amount of any discoloration to the UN dipped part.

If NO difference in color then oil is Inactive and would rate a ASTM D-130 of 1A. Color will vary from amber to black to red if "active".

Every one says new oils are inactive to copper that is true only when NEW as gear oils age/breakdown/oxidize and become contaminated they WILL become corrosive to copper with the
GL-5 type having about twice the S/P as a GL-4 they the GL-5 have more potential to corrode after breaking down and oxidizing.

Still that may still take 100K to do it tho.
Chevron's borate gear lubes will run >100K.

bruce