One of the most commonly asked questions regarding wear metal analysis is: “What do the spectrographic analysis numbers mean”?

This is a course subject on its own and will vary in every different type of unit. Mostly the concentrations of the elements are expressed in Parts Per Million (PPM) or occasionally as percentages. These elements will give us a guide to the origin of the wear metals. Very briefly, they go roughly like this:

Wear Metals

Iron. Cylinders, crank, gears, roller bearings, camshafts, gears, rings and valves.
Lead. Bearings (white metal), additives, bushing or petrol.
Tin. Bearings (white metal), bushing and piston skirts.
Copper. Bearings, bushes, thrusts washers, gears, brasses, bronzes and additives.
Aluminium. Pistons, washers, housings, bushing and clay dust.
Chromium. Hardening material from cams, rings, rollers, valves and shafts.
Nickel. Hardened or stainless steel shafts, valves and roller bearings.
Vanadium. Used with chrome coating and on valve stems etc.
Titanium. Aircraft components and lightweight, high strength parts.
Silver. Bearings, ring coating in some early engines and solder.

Contaminants

Silicon. Dust, sealant and gasket material, coolant and anti-foam additive.
Sodium. Coolant additive, salt water contaminant or detergent additive.

Additives

Additives are added to base oil to enhance the properties of the oil for different uses, hence are a helpful identifier to check for cross contamination and in some cases contamination levels.

Calcium. Usually high in engine oils as TBN, detergent or dispersant additives.
Magnesium. Detergent, dispersant additives (higher in engines).
Boron. EP and coolant additive.
Manganese. Detergent additive and lightweight metal.
Phosphorous. Anti-wear additive.
Molybdenum. Anti-wear additive with extremely low co-efficient of friction.
Zinc. Anti-wear, EP and anti-rust additive.
Sulphur. Naturally occurring in base oil, anti-wear additive, extreme pressure additive and combustion by-product.

Remember when interpreting spectrographic results, it is important to monitor the trend of the elements rather than the actual elemental levels. Check and stay below the manufacturer’s recommended limit but be alerted of a pending problem whenever wear trends move by more than 10% over similar oil hours.... always sample on a consistent and regular basis to maintain accurate trends - the key to a successful program.