ELEMENT OF THE MONTH
Each month we will explore elements of interest from the periodic table, with a brief history of discovery and development, and a review of uses and applications.
NICKEL – ATOMIC NUMBER 28
Nickel is a silvery metal with a slight yellow tinge, first isolated in 1751 from an impure nickel arsenide ore (niccolite), by Swedish chemist Baron Axel Cronstedt.
It is similar to iron in toughness and strength, but more like copper in its corrosion resistant properties, with relatively good thermal and electrical conductivity.
It is an irritant to human skin in the short term and can produce allergic reactions; it is a known carcinogen.
COMMON USES
As a Pure Element
In its pure state, it is used as a protective or barrier coating, typically deposited by a galvanic (electroplating) process.
It’s also used in solid electrical terminations where a temperature tolerance of up to 650 degrees C is required.
As an Alloy
An electroplated alloy coating of 85% zinc 15% nickel is widely used for corrosion protection of steel in automotive and aerospace applications, as an environmentally friendly alternative to cadmium, which is toxic, carcinogenic, and prohibited for most applications.
By far, the greatest use for nickel is in nickel-iron alloys such as stainless steels, where the nickel content can be between 5 and 15%. Higher nickel concentrations are found in corrosion resistant alloys such as Monel (~ 65% nickel 35% copper), and high temperature alloys such as Inconel 625 (~ 60% nickel 22% chromium + molybdenum, tantalum, and niobium).
Autocatalytic (electroless) nickel processes can deposit relatively hard and corrosion resistant nickel-phosphorous or nickel-boron alloy coatings that can extend the life and functionality of steel, copper, and aluminium alloys.
Where Is Nickel Used?
In general, nickel is used to improve the performance of a product, whether it is for the appearance or functionality. In either case, the final purpose of a product will be significantly influenced by the correct application of nickel, as a coating or in an alloy, and adherence to minimum and maximum tolerances in manufacture is critical.
QUANTIFYING NICKEL
Here are some key parameters for nickel measurements, using instruments from Helmut Fischer GmbH:
Thickness of nickel coatings – in the range of 0.1 to 35 µm, measurable using an instrument such as the Fischerscope XDL® 230/240
XDL® 230/240
Manual and programmable XYZ stage with a fixed 0.3mm diameter X-ray aperture. Cl (17) to U (92)
Thickness and phosphorous alloy composition of electroless nickel coatings – in the range of 0.1 to 40 µm, measurable using an instrument such as the Fischerscope XDAL® 237
XDAL® 237
Measurement of thickness and elemental composition [e.g. Ni% P% and NiP µm]. Significantly increased detection limits. Al (13) to U(92)
Composition Analysis and identification of solid nickel alloys, measurable using an instrument such as the Fischerscope XAN® 250
XAN® 250/252
High Performance XRF for fast material analysis and coating thickness. Al (13) to U (92).
The above methods use a non-destructive XRF technology for nickel coating thickness and alloy composition measurements.
Hardness and elastic modulus of nickel and electroless nickel coatings from 1 µm thickness and upwards
Measure these parameters perpendicular to the coating without the need for a micro-setcion, using Instrumented Indentation Hardness testing – only 10% of the coating thickness is penetrated
HM2000 AND HM500 NANOINDENTERS
Automatic and manual stage Nanoindenters with the load range of 0-2,000mN
APPLICATIONS
Automotive
Zinc-nickel anti-corrosion coatings on steel – coating thickness and % nickel are critical parameters, both accurately measurable using non-destructive XRF
Decorative chromium on nickel on copper on steel or plastic substrates – coating thicknesses are all critical for adhesion, brightness, and longevity of interior and exterior bright trims Thicknesses are measurable using destructive coulometry or non-destructive XRF
Aerospace
Zinc-nickel anti-corrosion coatings on steel – coating thickness and % nickel are critical parameters, both accurately measurable using non-destructive XRF
Decorative chromium on nickel on copper on steel or plastic substrates – coating thicknesses are all critical for adhesion, brightness, and longevity of interior and exterior bright trims Thicknesses are measurable using destructive coulometry or non-destructive XRF
Electronics
Electroless nickel barrier layer on printed circuit boards (PCB) – 2 to 5 µm thick to prevent intermetallic growth between copper PCB track and gold top layer – to maintain solderability. Thickness and % P composition measurable using non-destructive XRF
Electroless nickel anti-corrosion coating on aluminium connector shells – in the range 25 to 35 µm – Thickness and % phosphorous composition measurable using non-destructive XRF
Industrial, Oil, Gas and Offshore
High phosphorous content electroless nickel alloy in the range 25 to 40 µm with phosphorous content >10% for extreme corrosion resistance. Thickness and % P composition measurable using non-destructive XRF
Corrosion resistant Inconel cladding thickness on steel in the range of 5 to 15mm