Overview of oxidation laboratory tests on industrial lubricants part 1

Vincent Bouillon BFB – IESPM GROUP; Les Isnes (Gembloux) - BELGIUM INTRODUCTION

Developments in technologies and industrial material have led the additives and lubricants manufacturers to create higher performance lubricants. One of the key characteristics, besides anti-wear and EP resistance, good surface properties, and anti-corrosion protection is oxidation and thermal stability. There was a need to evaluate the performance of these oils using laboratory bench tests. The thermal and oxidation characteristics can be evaluated by many tests, some of which are detailed below. This paper relates to the following applications: • Hydraulic fluids • Turbine oils • Compressor oils • Industrial gear oils

Even if the control of fluid degradation including physico- chemical characteristics of the fluid as well as the monitoring of anti-oxidant depletion, the presence of degradations in the products is the key to detecting early stage of degradation and oxidation in order to avoid problems in the future. The very high quality level and performance of the formulated new oil remains essential.

The aim of this article is to give you an overview of existing laboratory oxidation tests and a guide to select the right test related to the application.


In an industrial lubrication system, the lubricant is submitted to a lot of constraints like a wide range of temperature, the presence of hot spots, the evaporation and sometimes several top-up; these severe service conditions lead formulators to search for thermo-stable base oils as well as the most efficient additives.

Base Oils

Lubricating base oils are mixtures of a large number of chemical compounds and are therefore characterised by the following

physico-chemical properties: viscosity and viscosity index (indicates viscosity-temperature relationship), specific gravity, cloud and pour point – flash, fire and auto-ignition point, aniline point, composition (content of paraffinic, iso-p., naphtenics, aromatics, saturates, sulphur), carbon residue, volatility, air release value, water separability, thermal stability, eco-toxicity and biodegradability.

API (the American Petroleum Institute) established five base oil categories based on sulphur and saturates concentrations and VI.

Group I contains oils that have >0.03% sulphur and 90% saturates by mass. These oils have a viscosity index in the range of 80-120. Group II and III oils, on the other hand, have 0.03% sulphur and 90% saturates by mass. However, they differ from each other in their viscosity index. The viscosity index for Group II oils ranges from 80-120 and viscosity index for Group III oils is 120. In general, Group II, Group III, and Group IV oils are low in aromatic and unsaturation. Hence, they oxidise at a slower rate than Group I oils which maintain a higher concentration in such structures. This is because such structures more readily form hydroperoxides and peroxy radicals that constitute the propagation stage of the oxidation process. Synthetic basestocks (Group V oils) have oxidation rates that vary because of varying structures. Alkylaromatics, for example, contain aromatic rings, and hence oxidise faster than ester basestocks, which in turn oxidise faster than olefin oligomers (PAOs) that belong to Group IV.



Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60