FILM-INFORMATION 1339488 - Caterpillar

Introduction
The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.Problem
Reports from the field indicate that the surface of the hydraulic cylinder rod may become gray or black. Certain affected machines may have hydraulic oil that contains an additional additive. The root cause of the discoloration of the hydraulic cylinder rod is being investigated.Solution
The discoloration may occur on the chrome coated surface of any hydraulic cylinder. The color of the rod can become blue, brown, or black. The color depends on the properties of the hydraulic oil and the additive package. The discoloration will remain unless the rod is polished with a buffing compound. The discoloration is usually less than one micron thick. The discoloration is due to one or more of the following parameters:
chemical reaction from the oil additives
mechanical system pressure
thermal existenceUnless buffing is done to the rod surface, the discoloration will remain permanently. The discoloration will not progress further.Replacement of the hydraulic cylinder rod is not recommended. The discoloration does not cause any operational problems to the machine performance.