ISO 6245:2001

Overview

ISO 6245:2001 specifies a standardized laboratory method for the determination of ash content in petroleum products. Applicable materials include distillate and residual fuel oils, crude petroleum, lubricating oils, waxes and similar products where ash-forming constituents are considered undesirable impurities or contaminants. The method covers ash contents in the range 0.001 % (m/m) to 0.180 % (m/m) and includes guidance on sampling, preparation, ignition and final muffle-furnace ashing.

Safety and good laboratory practice are emphasised: users must observe appropriate safety measures when handling flammable solvents, heating samples and operating high-temperature furnaces.

Key Topics

• Scope and exclusions: Not applicable to products that intentionally contain ash-forming additives (for some lubricating oils and additives use ISO 3987 which determines sulfated ash).
• Sampling: Samples shall be taken in accordance with ISO 3170 (manual) or ISO 3171 (automatic) where relevant, and homogenised before testing.
• Sample preparation: Procedures for mobile and viscous/solid samples are provided, including controlled heating to achieve homogeneity and steps to avoid loss of sample by foaming.
• Reagents and apparatus: Typical reagents include propan-2-ol and toluene (methylbenzene). Key apparatus items are an evaporating vessel (platinum, silica or porcelain), a muffle furnace capable of 775 °C ± 25 °C, an analytical balance (0.1 mg resolution) and a non-aerating mixer.
• Procedure summary: A measured test portion is burned to remove volatile organics; the carbonaceous residue is ashed in a muffle furnace at ~775 °C, cooled and weighed. Repeated heating/weighing cycles are used until consecutive weights agree within specified limits.
• Precision and expression of results: Results are reported to the nearest 0.001 % (m/m). Precision figures (interlaboratory) are given, e.g. repeatability/reproducibility for 0.001–0.079 % (r = 0.003, R = 0.005) and for 0.080–0.180 % (r = 0.007, R = 0.024).

Applications

• Quality control of fuels, crude and lubricants to detect contamination from metallic compounds, dirt or rust.
• Acceptance testing and batch verification where low ash content is critical to combustion, engine or process performance.
• Investigative testing where unexpected particulate deposits or corrosion products are suspected.

Practical benefits include consistent, repeatable ash quantification for compliance, troubleshooting and formulation control.

Related Standards

• ISO 3170 / ISO 3171 - sampling of petroleum liquids (manual and automatic).
• ISO 4259 - statistical treatment and precision data for test methods.
• ISO 5272 - specification for toluene used in laboratory reagents.
• ISO 3987 - determination of sulfated ash for lubricating oils and additives (used when additives affect ash behaviour).

For laboratory implementation, follow the full text of ISO 6245:2001 for detailed procedural steps, reporting requirements and safety notes.