Information from the Lubricants World

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Oxidation of Oil Products: What is Oxidation: Oxidation is a form of chemical deterioration that can occur in most organic materials. This can affect petroleum products but typically they are very resistant to oxidation. Oxidation usually involves the addition of oxygen atoms to the molecular structure and can result in degradation of the petroleum product involved. Signs of Oxidation: Increased viscosity of the petroleum product Formation of acrid odours Increase in Acid Number Formation of sludge, varnish, gums & acids Causes of Oxidation: Oxidation is promoted by: The presence of catalytic metals such as copper and iron, If your oil is working as a lubricant, copper can come from gears or bearing components. If your oil is working as cutting oil and you are machining one of the yellow metals i.e. copper, brass or bronze, that can be the source of copper. Either way, fine copper particles combined with iron particles in oil will accelerate the degradation of oil(s). Heat will also accelerate the degradation of oil and this will become significant once the heat exceeds 160°F/71°C. For every 18°F/10°C increase in temperature the rate of oxidation doubles. Peroxides and other organic acids which are the initial products of oxidation and are themselves, oxidizing agents. Moisture will also greatly accelerate oxidation. Entrained air usually from poor design will also contribute.

Oxidation of a petroleum product is a chain reaction. The farther it progresses, the more rapid it becomes and if left unchecked your oil could eventually form into a gel or solid varnish type material. In a screw machine application it can degrade to a level where it renders machinery to the point of being unusable. How Do We Measure Oxidation: Total Acid Number (TAN) is a measure of both the weak organic and strong inorganic acids present within oil. Testing for TAN is an essential preventative maintenance tool to maintain and protect your equipment. A rise in TAN is indicative of oil oxidation due to time, operating temperatures and contamination. Monitoring Trends as well as absolute values should be used to determine TAN levels. Prevention of Oxidation: You should always start with a high quality product that is suitable to your application. Everyone confuses the difference between cost and price. Price is what you pay for that barrel of oil today. Cost is that price plus all of the other unseen factors such as loss of efficiency, slower machining times, poorer surface finishes, premature replenishing and ultimately catastrophic failure of equipment. These are the hidden costs that build up everyday and can sometimes be almost invisible until your machinery comes to a grinding halt. The best way to prevent oxidation is to know what is going on in your oil system. If you want to start a regular program to ensure your lubricants are not oxidized you can do so by contacting your nearest Commonwealth Oil Distributor or by calling our Laboratory at 800-265-3698.