Overview
ISO 11998:2006 - Paints and varnishes - Determination of wet-scrub resistance and cleanability of coatings defines an accelerated laboratory method to evaluate how well a dry coating resists wear from repeated wet cleaning and how readily soils can be removed (cleanability). The standard specifies the test procedure, apparatus, reagents and reporting requirements; it notes that cleanability testing prescribes the method but not the specific soiling agents. Results are intended for comparison and classification under agreed limits (e.g., EN 13300), but are not directly transferable to all field conditions.
Key topics and technical requirements
- Test principle: apply a uniform coating on a defined test panel, condition and dry, then subject a defined area to 200 wet-scrub cycles using a reciprocating scrub tester. Determine mass loss and convert to mean loss in dry-film thickness.
- Reagents: washing liquid - a 2.5 g/L solution of sodium n‑dodecylbenzenesulfonate in laboratory-grade water (ISO 3696 grade 3).
- Apparatus & consumables:
- Film applicator (10–15 mm/s application speed).
- Reciprocating wet-scrub tester with stroke length (300 ± 10) mm and ~ (37 ± 2) cycles/min.
- Abrasive pad: non‑woven plastic with embedded abrasive, nominally (90.0 ± 0.5) mm × (39.0 ± 0.5) mm; new pad per test.
- Scrub pad holder mass: (135 ± 1) g.
- Test panels: PVC film substrate (nom. 0.25 mm) or alternative non-reactive substrate if required.
- Test procedure: wet the pad, apply washing liquid to the coating, run 200 cycles, rinse and dry to constant mass. Measure scrubbed area and mass loss.
- Results expression: loss in coating mass per unit area (g/m²) and mean loss in dry-film thickness (µm) using the measured dry-film density (method in Annex A).
- Precision: interlaboratory data reported repeatability ≈ ±18% and reproducibility ≈ ±30% (95% confidence, for the test conditions cited).
Applications and users
- Quality control and batch testing by paint and coating manufacturers (wet-scrub resistance classification).
- R&D teams developing scrub- and soil-resistant formulation improvements.
- Independent test laboratories performing comparative testing for specification compliance.
- Specifiers, architects, building contractors and facility managers assessing coatings for washable surfaces in healthcare, education, hospitality and commercial interiors.
- Certification bodies and standards committees referencing scrub resistance and cleanability classes.
Related standards
- ISO 1513, ISO 3270, ISO 3696 and ISO 15528 (referenced normative documents for sample prep, conditioning, water quality and sampling).
- Performance classification standards (for example EN 13300) commonly use wet-scrub data from ISO 11998 for class definitions.
Keywords: ISO 11998, wet-scrub resistance, cleanability, paint testing, coatings, scrub tester, abrasive pad, dry-film thickness, film applicator.
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