What are the drawbacks of using biodegradable lubricants?

Manufacturers and blenders promote these oils based on the importance of biodegradability and nontoxicity but few discuss the drawbacks of using biodegradable lubricants. Performance issues – such as oxidation stability, anti-wear protection, hydrolytic stability, viscosity stability at elevated temperatures and cost factors - are usually not discussed.

There are two primary classes of biodegradable lubricants; vegetable oils and synthetic lubricants, and industrial consumers of these products must be prepared to treat biodegradable lubricants somewhat
differently from standard mineral-base oils.

Drawbacks of using biodegradable lubricants derived from vegetable oils.

Vegetable biodegradable oils include corn, soybean, rapeseed (canola), sunflower, peanut, olive oil and others consist primarily of triglyceride molecular structures and as such have several performance limitations. Most notable of these limitations are poor thermal performance, hydrolytic and oxidation stability. For example, most natural vegetable oils cannot withstand reservoir temperatures greater than 80ºC.

In addition, water contamination, even in small quantities in the order of a few hundred parts per million, is one of the major drawbacks of using biodegradable lubricants derived from vegetable oils. This can cause serious foaming and degradation problems in operation.

Despite their good lubricating qualities, due to their polar nature which provides good metalwetting attraction making them good solvents for helping keep dirt and debris off metal surfaces, these oils exhibit poor low temperature flow capabilities.

Drawbacks of using synthetic biodegradable lubricants.

Synthetic biodegradable Oils include:

• Polyalphaolefins (PAOs) These exhibit excellent low-temperature properties, although they can be incompatible with certain seal materials and can shrink rubber seals. 
•  Diesters These have good antioxidation characteristics and seal swell properties. 
• Polyalkylene Glycols Also Known as Polyglycols or PAGs Drawbacks of using biodegradable lubricants in the PAG group are the tendencies to emulsify water in certain equipment, such as gearboxes. This will cause foaming, sludge formation and corrosion. Another major drawback of using biodegradable PAOs and PAG lubricants is their poor solubility with regard to additives. 

Because the additives themselves must also be biodegradable, this limits the additives that can be used to formulate effective biodegradable lubricants from PAOs and PAGs.

Today, some manufacturers are blending diesters with PAOs to form base oils which are biodegradable, have good solubility, resist oxidation and have good temperature viscosity characteristics. Others are blending synthetic diesters with canola oil to provide similar results.

Drawbacks of using biodegradable lubricants you need to consider before switching.

Obviously, biodegradable lubricants are ideal when used in certain resource industries, such as forestry, mining, petroleum exploration and farming - wherever the lubricants might come into direct contact with the environment.

The practical considerations associated with conversion from mineral-base lubricants to biodegradable fluids are however often ignored. These biodegradable lubricants are often different in their characteristics, and the conversion necessary for their effective use is not quite as simple as draining the used mineral oil and dumping in the new biodegradable lubricant.
 One of the most important disadvantages of using biodegradable lubricants that is frequently ignored, is whether or not the new biodegradable fluid is compatible with mineral oil. If not, serious problems could result if all of the old mineral oil is not thoroughly flushed from the system before the new fluid is installed.

Symptoms of a poor or incomplete conversion to biodegradable fluids include severe foaming; leaking seals, plugged filters, higher-than-normal wear on some components (such as the hydraulic pump), and increased operating temperatures.

With biodegradable lubricants, such as synthetic PAOs or vegetable oils costing three, four or five times the price of mineral oil it’s important to understand the drawbacks of using biodegradable lubricants. The professionals at Habot Synthetic Lubricants are well qualified to advise on the best application of any lubricant. Habot Synthetic Lubricants also produce high quality synthetic lubricants for automotive, mining, marine and industrial applications.