27 % Nickel-plated copper (NPC)

Nickel plating is applied to wire products due to its excellent corrosion resistance properties and in particular, its durability and stability at extremes of temperatures. Of significant importance, and a speciality product of LEONI Temco in the UK, is 27 % nickel-plated copper (NPC) – which provides unsurpassed levels of performance.The plating thickness of 27 % (by product weight) gives temperature protection of up to 750 °C, as well as providing superb corrosion resistance at negative temperatures such as those prevailing in the Stratosphere which can be as low as –60 °C. 27 % NPC is increasingly used in a wide range of applications and is included in aerospace, military and industrial/heating products.

Technical properties of nickel

  • Chemical element with symbol “Ni“
  • Specific weight 8.90 g/cm³ (at 20 °C)
  • Melting point is 1726 K (1453 °C)
  • Electrical resistivity 0.096 ohm mm²/m
  • Corrosion protection due to high resistance to environmental influences from alkalis, salt spray and reducing chemicals
  • High temperature resistance
  • Low hardness and good ductility in annealed condition

Nickel-plating at LEONI Temco

Commencing in the early 1950’s, LEONI Temco has a long and pioneering history in nickel-plating and in the processing of nickel-plated copper-based wire products. The technology has continually evolved in order to ensure the supply of top-grade nickel-plated products to satisfy market demands for consistent quality and high product reliability.

With the installation of Europe’s only nickel-plating line conceived and designed specifically for 27 % NPC wire, LEONI Temco has the unique capability of mass production of this technologically challenging material. Of course, the plating line is only the first part of the story; since its installation in 2007 a highly dedicated team of technologists has continually strived to keep improving the process. The plating chemistry has been carefully optimised, thus guaranteeing a nickel plating structure which is completely uniform and concentric. Process control is of paramount importance in ensuring the best nickel-plating quality for subsequent wire drawing. Due to the differences in hardness between the nickel plate and the copper substrate, ductility is a particularly critical aspect and is precisely managed – whilst simultaneously maximising the production capacity of this key machine.

Sophisticated testing techniques ensure that the plating chemistry and process controls are always optimally balanced, thereby depositing precisely the required quality and quantity of nickel – without variance – at any time throughout the lifespan of the electroplating solutions. Such monitoring also allows effective control of plating thickness within tight tolerances, which is an ever-present challenge for the conservation of resources and waste minimisation.

All of these efforts have proven successful in improving quality, capability and capacity well beyond the original design parameters of the equipment.

Advanced wire drawing processes

Once plated, the wire is readily drawn to fine diameters of as little as Ø 0.050 mm. The development work on plating has naturally also progressed to enhancing the wire drawing techniques. Drawing dies are strictly controlled and profiled with the very best of die measurement equipment to optimise the drawability of 27% NPC. Improvements in both the technologies and management systems for lubrication and filtration have also played a major role in effecting continual productivity improvements, notably with drawing speeds far in excess of anything deemed possible some years ago.

Annealing controls also provide the opportunity to adjust the temper of the finished wire, from fully annealed with excellent elongation, to customised intermediate tempers which maintain both flexibility and elongation, whilst retaining some additional tensile strength if needed for improved flex-life performance. This process capability has been particularly beneficial for producing braiding wire for applications ranging from traditional screening in external and non-pressurised sections of aircraft, to bonding leads for the Aerospace, Military and various Industrial markets.

Diverse range of 27 % NPC stranded products

At the opposite end of the scale to the fine-wire and its opportunities for miniaturisation, the core competency of stranding 27 % NPC wire is also continually developing. Multi-wire drawing is successfully employed as the basis for maximising capacity of higher-volume production of 27 % NPC wire and its subsequent stranding. The technology enables very consistent tension settings across all wires during drawing and at pay-off into the stranding machines. Exceptionally uniform stranded conductors - whether true concentric or unilay construction – is the result. Highly flexible bunches are similarly available, and for the more industrial applications, rope-strand constructions are manufactured as well. In addition to being a primary source within the European markets, LEONI Temco successfully exports the 27 % NPC products to international markets through its LEONI sister companies.

Standard range*

Applicable SpecificationASTM B355
Wire diameterØ 1,65 mm – Ø 0,050 mm
Wires for braiding2 to 12 wires
Stranded conductor0,05 mm² to 2,6 mm² 7, 19, 37 ends unilay or true concentric
Flexible bunch0,20 mm² – 2,5 mm²
Rope Strandsup to 25 mm²

Due to the superior corrosion and temperature resistance characteristics, demand for 27 % NPC continues to grow in a variety of industries. Within the Aerospace industry, 27 % NPC has particular importance – from traditional screening, to the currently evolving weight-reducing technologies for next-generation aircraft and power-plants.

*special sizes/constructions available on request.

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If you have not yet sourced 27 % NPC wires and strands from us, merely send us your product details and request a product qualification/quotation.