After visual evaluation and photography of the lid, the sampling tube and the sample bottle, we determine more than 20 elements for every lubricating grease sample. Along with wear and contamination particles, we examine the active ingredients and additives already present in the fresh grease. Using atomic emission spectroscopy (AES) with the rotating disc electrode method, in which a small amount of grease is applied to a target turntable, up to 21 elements are determined quantitatively and stated in the lab report in units of mg/kg (ppm). These values are divided into three categories: wear elements, contaminants and additives.
Iron, chromium, tin, copper, lead, nickel, aluminium, molybdenum and zinc, as well as concentrations of vanadium, titanium, silver, antimony, manganese and tungsten. Elevated iron and chromium values, for example, indicate wear of a rolling bearing. Copper and zinc indicate wear of a brass bearing cage.
Silicon, calcium, sodium, potassium, aluminium, cadmium and bismuth. Silicon (dust) and calcium (lime) in particular, as deposits from hard water, can promote wear. Sodium can also come from salt water and cause corrosion wear.
- Typical additives and thickeners:
Lithium, magnesium, calcium, phosphorus, zinc, barium, silicon, aluminium, molybdenum and boron. Their values are compared to those of the fresh grease. A change relative to a previous sample or the fresh grease can indicate mixing or reduced grease performance.