Overview
ISO 13805:1999 defines the spall test - an accelerated adhesion test for vitreous and porcelain enamel coatings on aluminium and aluminium alloys. The standard describes a laboratory method that exposes enamelled aluminium specimens to an electrolytic solution to assess the coating’s resistance to spalling (loss of enamel) caused by moisture or weathering. The greater the spalling observed in this test, the higher the likelihood of in-service failure due to poor adhesion.
Key topics and requirements
- Test principle: Immersion of a scored, enamelled specimen in an aqueous solution of antimony trichloride (SbCl3) to promote spalling where adhesion is weak.
- Test solution: Prepare an aqueous solution of SbCl3 at 10 g/l; a fresh solution is prepared on the day of testing. Note: SbCl3 is hygroscopic and must be stored sealed.
- Conditions: Ambient temperature 18 °C to 28 °C, test duration 20 hours.
- Specimen preparation: At least one cut edge (≈90° to the surface) and a cross score extending to the base metal; file from enamel to metal if refinishing. Clean and degrease prior to test.
- Cleaning reagent: Sodium n‑alkyl (C10–C13) benzene sulphonate at 0.1% active substance in distilled or demineralized water; immersion ≈ 40 °C for 3 minutes then rinse.
- Apparatus: Balance, graduated cylinder (1 000 ml), beaker or plastic vessel, plastic/glass hook or stand, viscose sponge, file, steel needle.
- Specimen immersion volume: At least 3 ml of test solution for each cm of specimen surface area (as specified in the standard).
- Post-test inspection: Rinse, remove loose enamel with a viscose sponge, air dry and perform a visual examination from 250 mm.
- Failure criteria: The standard lists size/location thresholds for spall areas (e.g., visible base metal spall >25 mm located >3 mm from an edge or score; isolated spall areas exceeding a given area; multiple spall areas per dm2) that determine whether the specimen is judged to have failed.
Applications and users
ISO 13805 is used for:
- Quality control and batch testing of porcelain enamel coatings on aluminium
- R&D and formulation development of enamels and pretreatment processes
- Comparative evaluation of aluminium alloys and pre-treatment methods for enamel adhesion
- Acceptance testing by manufacturers, coating suppliers, test laboratories, OEMs and specifiers for appliances, cookware, architectural panels and other enamelled aluminium products exposed to moisture or weathering
Keywords: ISO 13805, spall test, porcelain enamel, aluminium, adhesion test, SbCl3, accelerated weathering.
Related standards
- ISO 10141 - Vitreous and porcelain enamels - Vocabulary
- ISO 13804 - Production of specimens for testing (enamel on aluminium)
- ISO 3819, ISO 4788 - Laboratory glassware (beakers, graduated cylinders)