Overview
EN ISO 28706-5:2011 (ISO 28706-5:2010) defines a laboratory test method for determining the resistance of vitreous and porcelain enamels to chemical corrosion in closed systems. It is intended primarily for enamels used in chemical-process environments where liquids act on enamel surfaces under closed/high-temperature conditions (autoclaves). The standard supersedes EN 14483-5:2004 and is part of the ISO 28706 series on corrosion testing of enamels.
Key Topics
- Scope and principle: assessment of enamel dissolution by acids, neutrals and alkalis in closed systems; attack is quantified by mass loss and, where appropriate, corrosion rate.
- Apparatus and autoclave testing: test equipment and autoclave procedures for high-temperature, pressurized exposure to aggressive media to avoid inhibition effects.
- Test specimens and preparation: specimen selection, surface preparation and area measurement requirements.
- Test procedures: specified exposure conditions (including a short high-temperature autoclave regime-typically limited to 24 h to avoid inhibition), liquid-to-surface ratios and solution preparation with low‑silica water when required.
- Specific tests:
- Autoclave test with hydrochloric acid (example of linear attack enabling corrosion-rate calculation).
- Test with hot sodium hydroxide solution (alkaline attack behaviour).
- Simulated solutions and actual process fluids (customized testing using process mixes representative of service conditions).
- Expression of results: loss in mass per unit area (g/m2) and, when attack is linear, rate of loss in mass per unit area and corrosion rate (mm/year).
- Limitations and notes: different firing temperatures (e.g., enamels fired below 700 °C) may require alternative test parameters; safety warning about hazardous chemicals and procedures.
Applications
- Material selection and qualification for chemical‑process equipment (reactors, tanks, heat exchangers) lined with vitreous or porcelain enamel.
- Quality control and batch acceptance testing by enamel manufacturers and coating suppliers.
- Independent laboratory testing, failure analysis and verification for plant operators, OEMs and specifiers.
- R&D for new enamel formulations and process compatibility assessments with real process fluids.
Who Uses This Standard
- Enamel manufacturers and formulators
- Industrial coating and surface‑treatment laboratories
- Chemical plant engineers and asset owners
- Procurement, QA/QC and regulatory compliance teams
- Standards committees and certification bodies
Related Standards
- Other parts of ISO 28706 (Parts 1–4) covering room‑temperature acids, boiling acids/neutrals, and alkaline tests using various vessel geometries.
- EN 14483-5:2004 (superseded)
Keywords: EN ISO 28706-5:2011, vitreous and porcelain enamels, chemical corrosion, closed systems, autoclave test, corrosion resistance testing, hydrochloric acid, sodium hydroxide, process fluids.
