Hydraulic Fluids
Background & Properties
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May 2025
GPS
Industry Specifications
Environmental Tests
OECD 301B
Biodegradability test that measures how long it takes for a substance to totally biodegrade into carbon
dioxide gas and water. More severe than CEC L-33 T 82.
CEC L-33-T-82
Biodegradability test that measures only the first step in the biodegradation process. Is an alternative to
OECD 301B.
Importance of Corrosion and Rust Tests
Keeping hydraulic systems clean is important to an efficient operation. Corrosion and rust can occur from the
presence of oxygen or water. Hydraulic fluids need to protect against these contaminants with rust and
corrosion inhibitors formulated in the fluid, and protect metallic surfaces. Rust and corrosion will affect pump
performance and can lead to hydraulic pump failures.
Types of Corrosion and Rust Tests include:
Rust Prevention (D665 -06 A & B)
Standard test method for rust-preventing characteristics of lubricants in the presence of water. Method A uses
distilled water, Method B uses salt water, so method B is more severe.
Steel Corrosion (ASTM D 665)
is test is performed with distilled water and synthetic seawater. It measures the hydraulic fluid's ability to
protect against rust and corrosion when contaminated with water.
Test Criteria
Distilled Water Pass/Fail
Synthetic Sea Water Pass/Fail
Once again, this is a very important test for hydraulic fluids that must protect equipment in the presence of
water. Some additives in lesser quality hydraulic fluids may become corrosive when exposed to water.
Copper Strip (ASTM D 130)
Test Criteria
DIN 51524 Part 2 2 max
GM (LS-2) LH, 03, 04, 06 1b max
C8
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