ISO 15724:2001

Overview

ISO 15724:2001 - Metallic and other inorganic coatings - Electrochemical measurement of diffusible hydrogen in steels - Barnacle electrode method - defines a rapid, comparative electrochemical test for diffusible hydrogen in carbon and alloy steels. The method uses a barnacle electrode (a small cell with a Ni/NiO cathode and 0.2 M NaOH electrolyte) to oxidize mobile hydrogen at the steel surface and records the oxidation current density vs time. ISO 15724:2001 measures relative hydrogen levels (not absolute concentrations) and is intended for quality control and monitoring of hydrogen uptake during plating, corrosion, or heat treatments.

Key Topics and Requirements

• Scope & limitations
  • Applies to carbon and alloy steels (excludes austenitic stainless steels unless kinetics are separately established).
  • Intended for flat specimens (slightly curved or small parts need adapted procedures).
  • Measurements at room temperature (25 °C ± 1 °C) and for a fixed time (typically 30 min).
• Principle
  • Steel specimen acts as the anode; Ni/NiO electrode as cathode. Oxidation current is attributed to mobile hydrogen escaping to the surface.
  • Results are comparative; higher current densities indicate greater likelihood of hydrogen embrittlement.
• Apparatus & reagents
  • Barnacle cell with silicone gasket (typical contact area ≈ 1 cm²), Ni/NiO electrode (≈5× anode area), 0.2 M NaOH electrolyte, electrometer/recorder and known resistance.
  • Reagents include methyl or ethyl alcohol for cleaning.
• Calibration & procedure
  • Ni/NiO electrode must be calibrated vs saturated calomel electrode (SCE) and recharged when potential drops below ~300 mV more noble than SCE.
  • Specimen prep: light abrasion, solvent wipe; plated parts require coating removal by a method proven not to introduce hydrogen.
  • Start measurement within short, specified time windows (assembly and start limits provided in the standard).
• Data interpretation
  • Background current densities are established on hydrogen-free specimens. Measurement differences provide a relative assessment of diffusible hydrogen and treatment effectiveness.

Applications and Users

• Quality control in electroplating shops, surface-coating and finishing operations.
• Metallurgists, corrosion engineers, failure-analysis labs and R&D teams monitoring hydrogen uptake, verifying pre- and post-plating heat treatments, or screening parts for susceptibility to hydrogen embrittlement.
• Useful for rapid process control and comparative tests rather than establishing absolute hydrogen content.

Related Standards

• ISO 9587 - Pretreatments to reduce hydrogen embrittlement risk
• ISO 9588 - Post-coating heat treatments to reduce hydrogen embrittlement
• ISO 10587 - Inclined wedge method (for correlating susceptibility data)

Keywords: ISO 15724:2001, barnacle electrode method, diffusible hydrogen, hydrogen embrittlement, electrochemical measurement, Ni/NiO electrode, plating quality control.