Overview
ISO 28706-5:2010 - "Vitreous and porcelain enamels - Determination of resistance to chemical corrosion - Part 5: Determination of resistance to chemical corrosion in closed systems" - specifies a laboratory test method for assessing the chemical corrosion resistance of vitreous and porcelain-enamelled articles when exposed to acid, neutral and alkaline liquids (including real process mixes) under closed-system/autoclave conditions. It is intended mainly for enamels used in chemical process equipment and gives procedures to measure mass loss and calculate corrosion rates where appropriate.
Key topics and technical requirements
- Test principle: Enamelled specimens are exposed to corrosive liquids at temperatures above their normal boiling point in a sealed vessel; mass loss is measured to assess attack.
- Test vessel design: Volume-to-exposed-area ratio V/A = (40 ± 2) cm (V in cm³ at 20 °C, A in cm²). Vessel must leave at least 20% headspace at 18–28 °C.
- Materials and fittings: Vessel materials must resist test solutions and not release interfering species (avoid glass/ceramic for some acids; PTFE permitted for seals; tantalum recommended for aggressive acids).
- Heating and control: Test temperature should be reached within 1 hour and controlled to within ±1 °C (temperature defined at the enamel interface).
- Specimen limits: Individual specimen mass ≤ 160 g; area-to-mass ratio A/m > 0.1 cm²/g. Enamel must fully cover specimens and reflect production processes.
- Equipment: Analytical balance (±0.02 mg), oven (≥120 °C), desiccator, hydrometer (ISO 649-1 compliant).
- Results reporting: Loss in mass per unit area is determined; where attack is linear, a rate of loss and corrosion rate can be calculated. Test times and conditions must be recorded.
Applications and users
ISO 28706-5:2010 is practical for:
- Manufacturers of chemical process vessels, reactors, heat exchangers and storage tanks with enamel linings.
- Quality control, R&D and materials engineering teams evaluating enamel formulations for resistance to specific process fluids.
- Inspection labs and third-party testing facilities performing standardized corrosion testing for procurement or certification.
- Process engineers assessing suitability of enamelled components for acidic, neutral or alkaline closed-system service (autoclave/pressurized environments).
Keywords: ISO 28706-5:2010, vitreous and porcelain enamels, chemical corrosion, closed systems, autoclave testing, corrosion rate, enamelled articles.
Related standards
ISO 28706 is a multi-part series on enamel corrosion testing:
- Part 1 - acids at room temperature
- Part 2 - boiling acids/neutral liquids and vapours
- Part 3 - alkaline liquids (hexagonal vessel)
- Part 4 - alkaline liquids (cylindrical vessel)
Refer to these parts for complementary methods and for tests under different temperature and exposure regimes.
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