ASTM D6304

Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration

Applicability: Applies to petroleum products, lubricants, base oils, fuels, and additives in which trace water must be accurately quantified, typically in the range of 10 to 25,000 mg/kg. Particularly suited for samples with low water content where the volumetric Karl Fischer method would lack sufficient precision. Not appropriate for samples containing strong reducing or oxidizing agents that could interfere with the electrochemical iodine generation.

Purpose: Quantifies trace water content using coulometric Karl Fischer titration, in which iodine is electrochemically generated in situ in direct proportion to the water present in the injected sample, eliminating the need for a separately standardized reagent solution. The technique provides improved accuracy at low moisture concentrations compared to volumetric methods. Results are used for quality control and specification compliance of lubricants and fuels, where excess moisture causes corrosion, emulsification, and premature additive breakdown.