To: Golden Rivet and all
Golden Rivet said:
“The 757 truck pivot pin uses ROYCO 11MS which equates to MIL-G-7711A+MoS2 for those of you with an inquisitive nature. According to the ROYCO web site it is a general-purpose extreme pressure lubricant. Don't think it contains any Molybdenum Di Sulfide”.
Response: Here is the spec you referenced, taken directly from the ROYCO web site and it is exactly as you stated. However it does contain Molybdenum Di Sulfide which has a chemical symbol of MoS2.
(ROYCO 11MS MIL-G-7711A+MoS2 Aircraft general-purpose extreme pressure grease).
This may be the cause of the corrosion on the subject pin. The US Military banned the use of Mo S2 from, use on their air vehicles. Molybdenum Di Sulfide when in contact with a warm saline environment will degenerate into Hydrochloric and Sulfuric acid. The major lubrication suppliers re-compounded the Mo S2 to contain an inhibitor to keep the degeneration from happening. The inhibitor can weaken and not prevent the decomposition process. It is imperative that you and all users of this lubricant check to see if the inhibitor is added and if not discontinue the use of the product. If the inhibitor is added then check to see if it is in fact losing efficacy and if so then consult Boeing to see if the lubrication schedule can be changed to minimize the degradation of the inhibitor by replacing the grease at a higher frequency than specified in the maintenance manual.
Does anyone have a teapot as I believe this will cause a tempest?