ISO 12137:2011

Overview

ISO 12137:2011 - Paints and varnishes - Determination of mar resistance - defines a laboratory test method to assess the mar resistance of a single coating or the upper layer of a multicoat system using a curved (loop-shaped or ring-shaped) stylus. The standard is intended for comparative testing and provides relative ratings for coatings that show significant differences in susceptibility to mar. It complements, but does not replace, pointed-stylus methods described in ISO 1518‑1 and ISO 1518‑2.

Key Topics and Requirements

• Test principle: A loop- or ring-shaped stylus mounted at a 45° angle is pressed onto a coated test panel while the panel is moved beneath the stylus. Load is increased in steps until marring occurs.
• Instrument and stylus:
  • Balanced-beam mar-resistance instrument with capacity up to 5 kg and step resolution typically 0.5 kg (0.25 kg or 0.1 kg allowed for higher accuracy).
  • Loop stylus: chromium-plated steel, 1.6 mm rod bent into U-shape, outside radius (3.25 ± 0.05) mm, hardened to Rockwell HRC56–58, surface roughness