Overview - ISO 28706-4:2016 (Vitreous and porcelain enamels, alkaline corrosion test)
ISO 28706-4:2016 specifies a laboratory test method to determine the resistance of vitreous and porcelain enamelled articles to attack by alkaline liquids (e.g., sodium hydroxide) using a cylindrical vessel. The method covers testing at temperatures between 25 °C and 95 °C, using a vessel designed to test a single enamelled specimen. Although originally developed for hot NaOH solutions, the standard permits testing of other alkaline media and is commonly applied to enamels used in the chemical industry.
Key topics and technical requirements
- Scope and purpose: Evaluate chemical corrosion of enamel coatings by alkaline liquids under controlled temperature and time.
- Test principle: Expose a single enamelled specimen to an alkaline solution in a cylindrical vessel; the solution is static (not stirred).
- Apparatus and materials: Specifies use of a cylindrical test vessel and references normative laboratory equipment standards (volumetric glassware, laboratory water quality, etc.).
- Reagents and test solutions: Clauses define common test solutions - notably 0.1 mol/l NaOH and 1.0 mol/l NaOH - and permit other alkaline media where appropriate.
- Specimen preparation: References production and handling of test specimens (see normative reference ISO 28764 for specimen production on different substrates).
- Test conditions: Temperature control between 25 °C and 95 °C; clauses set the required temperatures and durations for specified NaOH tests.
- Measurement and expression of results:
- Total loss in mass per unit area (g/m²) after exposure.
- Corrosion rate (e.g., mm/year) when mass loss proceeds linearly with time.
- Reporting: Test report must include solution composition, temperature, duration, specimen details and measured corrosion values.
- Safety note: The standard warns users to apply appropriate health, safety and environmental controls when handling alkaline reagents.
Applications and who uses this standard
- Manufacturers of enamelled vessels, piping, tanks and reactors, especially for the chemical process industry.
- Quality control and R&D laboratories assessing enamel formulations, firing processes, and coating durability.
- Materials engineers and corrosion specialists who need standardized, comparable data on enamel resistance to caustic media.
- Regulatory bodies and procurement teams specifying performance criteria for enamelled equipment exposed to alkaline service.
Related standards
- Other parts of ISO 28706 series: Part 1 (acids, room temp), Part 2 (boiling acids/neutral liquids), Part 3 (alkaline liquids using a hexagonal vessel), Part 5 (closed systems).
- Normative references cited in ISO 28706-4: ISO 48, ISO 1042, ISO 3696, ISO 28764, EN 10088-1.
Keywords: ISO 28706-4:2016, vitreous and porcelain enamels, chemical corrosion, alkaline liquids, cylindrical vessel, sodium hydroxide, corrosion rate, enamel testing.