Acid Number Explained by Eurofins TestOil

Are you 100% sure you know what AN (acid number) measures and what it reveals? Actually A LOT of things! Acid number measures acidic components in the oil sample. These can include degradation products such as organic acids, esters, and salts as well as contaminants such as inorganic acids, and certain additives such as detergents and inhibitors. 

                So, on one level AN just measures acid—more importantly,  AN will let you know if you need to take a harder look at what may be causing the acid—serious issues can stem from antioxidant depletion. When antioxidants have been consumed, oxidation of the lubricant will ensue, producing acidic compounds and increasing the acid number.

                There is a misconception that AN just detects the lubricant’s level of acidity, but it goes beyond that to detecting the concentration of specific acids present in the lubricant-both weak organic acids and strong inorganic acids. Pinpointing the concentration of acidic contaminants allows for understanding the extent of additive depletion, a change in oil type, or degradation.

                The acidic byproducts formed due to oxidation can lead to machine damage stemming from corrosive wear. Acidic conditions can result in corrosion of machine components. High acid number due to lubricant degradation products can also promote accelerated lubricant degradation and may contribute to formation of sludge or varnish. Monitoring the AN and taking action can head all this off.

                AN measurement involves diluting a portion of the sample and then titrating it with a basic solution to a specific endpoint (ASTM method-D974). The result expresses how much titrant is needed to neutralize the acids in the sample aliquot.

                All industrial lubricating oils and some combustion engine oils are excellent candidates for AN. However, this test is not appropriate for high water content fluids such as water glycols and oil/water emulsions. Monitoring other parameters such as viscosity and FTIR oxidation along with acid number can provide a more complete picture of the lubricant condition. 

For more information on working with Eurofins TestOil for oil analysis programs or training opportunities, fill out the form below; visit https://testoil.com/company/contact-us/; call 216-251-2510; or email sales@testoil.com.

About Eurofins TestOil

With more than 30 years of experience in the oil analysis industry, Eurofins TestOil focuses exclusively on assisting industrial facilities with reducing maintenance costs and avoiding unexpected downtime through oil and fuel analysis program implementation. As industry experts in diagnosing oil-related issues in equipment such as turbines, hydraulics, gearboxes, pumps, compressors and diesel generators, Eurofins TestOil provides customers with same-day turnaround on routine oil analysis testing.  For more information on partnering with Eurofins TestOil on oil analysis programs or training opportunities visit https://testoil.com. Contact: Al Yates 216-251-2510; sales@testoil.com. 

About Eurofins – the global leader in bio-analysis

Eurofins is Testing for Life. Eurofins is the global leader in food, environment, pharmaceutical and cosmetic product testing, and in discovery pharmacology, forensics, advanced material sciences and agroscience Contract Research services. Eurofins is also a market leader in certain testing and laboratory services for genomics, and in the support of clinical studies, as well as in BioPharma Contract Development and Manufacturing. The Group also has a rapidly developing presence in highly specialised and molecular clinical diagnostic testing and in-vitro diagnostic products.

With over 61,000 staff across a network of 940 laboratories in 59 countries, Eurofins’ companies offer a portfolio of over 200,000 analytical methods. Eurofins Shares are listed on Euronext Paris Stock Exchange.