Overview
ISO 2179:1986 specifies the requirements for electroplated coatings of tin-nickel alloy (SnNi), with a composition of approximately 65% tin and 35% nickel. This standard defines classification, thickness, appearance, testing, and performance criteria for such coatings on both ferrous and non-ferrous substrates, as well as on printed circuit boards. Notably, it does not apply to threaded components, unfabricated sheet, strip or wire, coil springs, or steels with tensile strength over 1,000 MPa. The standard also outlines the information purchasers must specify to ensure appropriate application and quality control of tin-nickel electroplated coatings.
Key Topics
- Material Composition: Specifies SnNi alloys at ~65% tin, ~35% nickel.
- Applicable Substrates: Ferrous, non-ferrous metals, and printed circuit boards.
- Exclusions: Threaded components, unfabricated materials, coil springs, and certain high-strength steels.
- Coating Classification: Based on service condition and minimum coating thickness.
- Undercoat Requirements: Guidance for substrates that require underlayers (such as copper or nickel).
- Testing and Verification: Emphasizes methods for verifying adhesion, coating thickness, and porosity.
- Purchaser's Role: Clearly defines the information the purchaser must supply for successful coating specification.
Applications
Electroplated tin-nickel coatings as defined in ISO 2179:1986 are used in a variety of industrial and technical applications where wear resistance, corrosion resistance, and high-quality surface finish are essential. Common applications include:
- Electronic components: SnNi coatings provide corrosion protection for connectors, terminals, and printed circuit boards without the risk of whisker growth often associated with pure tin plating.
- Mechanical parts: Used where a hard, wear-resistant, and corrosion-resistant coating is required on metal parts, especially those operating under mild to severe service conditions.
- Aerospace, automotive, and precision engineering: Chosen for their excellent passivation, oxidation resistance, and compatibility with various base materials.
- Specialized fasteners and connectors: While not intended for threaded components, ideal for non-threaded elements requiring reliable electroplated finishes.
Note: The standard outlines that coatings should generally not be applied to parts expected to undergo deformation or vibration after plating due to the inherent brittleness of the alloy.
Related Standards
Implementing ISO 2179:1986 often involves cross-referencing related ISO standards for testing, measurement, and quality control:
- ISO 1462 - Accelerated corrosion tests for metallic coatings.
- ISO 1463 - Measurement of coating thickness by microscopic method.
- ISO 2177 - Measurement of coating thickness by coulometric (anodic dissolution) method.
- ISO 2664 - Definitions for thickness measurements and conventions.
- ISO 2859 / ISO 4519 - Sampling procedures for inspection by attributes.
- ISO 3497 - X-ray spectrometric methods for coating thickness measurement.
- ISO 6988 - Testing for sulfur dioxide corrosion with moisture.
Purchasers and specifiers are encouraged to consult these related documents for comprehensive guidance on testing methods and acceptance criteria.
Practical Value
By following ISO 2179:1986, manufacturers and users ensure that tin-nickel electroplated coatings meet consistent, internationally acknowledged criteria for performance and reliability. The standard also supports effective communication between purchasers and suppliers, guaranteeing that end-use requirements like thickness, service environment, and substrate compatibility are defined and controlled, minimizing defects and ensuring product longevity. Proper adoption of this standard helps industries maintain high-quality surface finishes, corrosion protection, and overall component durability in demanding applications.