Overview
EN ISO 16866:2022 (ISO 16866:2020) specifies the STEP test - Simultaneous Thickness and Electrode Potential determination - for electroplated multilayer nickel coatings. The standard defines a validated method to measure, in a single operation, the individual layer thicknesses and the electrode potential differences between layers in multilayer nickel deposits. Measurement of coatings other than electroplated multilayer nickel systems is explicitly outside the scope.
Key topics and technical requirements
- Test principle: A modification of the coulometric (anodic dissolution) thickness measurement that records potential jumps against a reference electrode as each nickel layer dissolves.
- Measuring cell designs: Two typical cell configurations are described - a silver wire coated with AgCl positioned at the cell edge, and a silver ring coated with AgCl at the cell base. Both give comparable uncertainty after calibration.
- Instrumentation: Requires a measuring instrument with a constant-current source and voltmeter, appropriate pump/circulation for electrolyte and a stable reference electrode.
- Accuracy factors: The standard addresses influences on measurement uncertainty, including electrolyte composition, conditioning, surface cleanliness, measurement area and contact pressure, electrical contact, and complete dissolution of layers.
- Evaluation & reporting: Procedures for measurement, evaluation, uncertainty assessment and required elements in the test report are defined.
- Practical benchmark values: The document notes common observed potential differences (e.g., ~80–150 mV for typical double nickel layers; ≳20 mV between bright nickel and special nickel layers), while not mandating fixed acceptance limits.
- Normative references: Includes ISO 2177 (coulometric thickness measurement) and ISO 3696 (laboratory water quality).
Applications
- Quality control of electroplated multilayer nickel systems in manufacturing (e.g., automotive, electronics, decorative and functional plating).
- Corrosion assessment by determining potential differences that influence galvanic behavior between nickel layers.
- Failure analysis and process troubleshooting where layer integrity or unexpected electrochemical behavior is suspected.
- Contract and specification verification where documented layer thickness and interlayer potentials are required.
Who should use this standard
- Plating laboratories and quality assurance teams
- Corrosion engineers and materials scientists
- Automotive and electronics manufacturers with multilayer nickel plating processes
- Test laboratories seeking standardized methods for thickness and electrochemical characterization
Related standards
- ISO 2177 - Metallic coatings: Coulometric method by anodic dissolution (thickness)
- ISO 3696 - Water for analytical laboratory use (quality of electrolyte)
- EN ISO 16866:2022 supersedes EN 16866:2017 and is the adopted European version of ISO 16866:2020.
Keywords: EN ISO 16866:2022, STEP test, multilayer nickel deposits, nickel coatings, electrode potential, thickness measurement, coulometric method, electroplated nickel.
