Overview
EN ISO 8289-2:2019 (ISO 8289-2:2019) specifies a low-voltage slurry test for detecting and locating defects (pores, cracks, pop-offs) in vitreous and porcelain enamel coatings on profiled surfaces such as corrugated or undulated metal sheets. The method is an optical low-voltage test that uses a conductive slurry to reveal defects that extend down to the metal substrate. It is a non-destructive inspection technique intended for precise defect detection and positional mapping.
Key topics and technical requirements
- Test principle: Optical colour-effect detection using a conducting liquid (slurry) under low DC voltage.
- Test medium (slurry):
- Base ingredients: titanium dioxide (anatase), pyrogenic silicic acid, quartz, polysaccharide, sodium chloride solution and an alcoholic phenolphthalein solution.
- Typical formulation: prepared by intensive grinding of specified parts by mass with a combined saline/phenolphthalein solution; adjusted to a specific gravity of (1.1 ± 0.1) g/cm³.
- Conductivity: (0.475 ± 0.025) S/m; pH: (8 ± 0.5).
- Storage: slurry storage limited to about three months; caution handling phenolphthalein.
- Apparatus:
- DC power source adjustable between 10 V and 24 V (±1 V); stabilized supply with digital display recommended.
- Metal “broom” electrode as anode (positive); specimen substrate connected as cathode (negative).
- Procedure:
- Clean and mask the test area, spray slurry to form an even film, connect electrodes, apply typically 12 V for 1 minute, then count defects within 1 minute after switching off.
- Defects appear as visibly red spots in the white slurry.
- Evaluation and reporting:
- Defect density reported as number per square metre (N = S / A).
- Test report to reference ISO 8289-2 and include article ID, defect count/location, slurry formulation and test date.
Applications and users
- Primary applications:
- Quality control and inspection of enamelled corrugated/undulated sheets (e.g., heat exchanger components, decorative and functional enamelled metal products).
- Incoming inspection, production-line checks, and failure analysis where positional mapping of defects is required.
- Who uses it:
- Enamel manufacturers, metal coating specialists, heat-exchanger fabricators, independent testing laboratories, and product conformity assessors.
Related standards
- ISO 2746 - high-voltage test for enamel defects (different, destructive principle).
- ISO 19496-1 - terminology for vitreous and porcelain enamels.
- Adopted as EN ISO 8289-2:2019 by CEN (European national standards bodies).
Keywords: vitreous and porcelain enamels, low-voltage test, slurry test, profiled surfaces, corrugated enamel, defect detection, ISO 8289-2:2019, enamel quality control.