Materials Compatibility

Materials used in the hydraulic system and surrounding it must be compatible with the hydraulic fluid. The fluid must not degrade their performance; neither should the materials degrade the fluid. The materials and components used in and near any aircraft hydraulic system are carefully selected by the airframe manufacturer. The aircraft industry uses many synthetic materials – many are resistant to Skydrol fluids and some are not. Many that are not totally resistant require long exposure before damage results.Deviations from the recommended materials should not be made without prior consultation with the airframe manufacturer and the materials components suppliers. The table below contains the general rating of compatibility of various materials with Skydrol fluids.

General Guidelines for Compatibility of Aviation
Phosphate Ester Hydraulic Fluids with Various Materials*

Ratings of Compatibility
EXCELLENT RESISTANCE – Material may be used in constant contact with the fluid.
GOOD RESISTANCE –Withstands exposure to the fluid with minimum swell (for plastics and rubber) or loss of integrity.
POOR RESISTANCE – Should not be used near the fluid.
NO RESISTANCE – Disintegrates in the fluid.