Nickel Nitrate (CAS 13478-00-7): Applications in Electroplating and Catalyst Preparation

Nickel nitrate hexahydrate, Ni(NO₃)₂·6H₂O (CAS 13478-00-7), is a green crystalline inorganic salt that serves as one of the most versatile soluble nickel sources in industrial chemistry. With a purity of ≥ 98.0% and tightly controlled impurity levels, high-grade nickel nitrate is a preferred raw material in two demanding sectors: electroplating and catalyst manufacturing. This article examines how nickel nitrate is used in each application and what purity requirements determine performance.

What Is Nickel Nitrate?

Nickel nitrate is the nickel(II) salt of nitric acid. In its commercially traded hexahydrate form, it contains six molecules of water of crystallisation, giving it a characteristic bright green colour and a melting point of approximately 57 °C. It is highly soluble in water and polar solvents, making it straightforward to formulate into aqueous process baths and impregnation solutions.

Unlike nickel sulfate — the dominant nickel salt in electroplating — nickel nitrate introduces the nitrate anion (NO₃⁻) into the bath, which plays a distinct electrochemical role. Unlike nickel chloride, it introduces no halide contamination. This combination of properties makes nickel nitrate a specialised but important component in several process chemistries.

Electroplating Applications

Watts Bath and Functional Nickel Plating

The standard Watts nickel bath — the workhorse of the electroplating industry — is formulated with nickel sulfate as the primary nickel source and nickel chloride as an anode activator. Nickel nitrate is added to specific Watts-type bath formulations as an oxidising depolariser at the cathode. The nitrate ion undergoes partial electroreduction, which raises the cathode current efficiency, reduces hydrogen evolution, and improves deposit brightness and levelling at higher current densities.

In functional engineering nickel plating — where the deposit must provide wear resistance, hardness (typically 150–500 HV), and corrosion protection — nickel nitrate addition helps maintain consistent deposit microstructure across complex geometries with varying local current density. This is particularly relevant for automotive components, hydraulic actuators, and industrial tooling where uniform coating thickness is a quality requirement.

Decorative Nickel Plating

Decorative nickel underlayers — applied beneath chromium, gold, or palladium topcoats on sanitary fittings, automotive trim, and consumer electronics housings — require smooth, bright, low-stress deposits free of pitting and roughness. Pitting arises primarily from bath contamination by organic decomposition products, metallic impurities, and particulate matter.

The use of high-purity nickel nitrate with Fe ≤ 0.001%, Cu ≤ 0.005%, and Zn ≤ 0.01% is essential in decorative applications. Iron contamination at even 5–10 ppm in the bath causes dark, stressed deposits; copper co-deposition creates colour inconsistency; zinc causes brittleness. By selecting a nickel nitrate grade with tightly controlled metallic impurities, platers reduce bath correction frequency and reject rates.

Electroless Nickel Plating

Autocatalytic (electroless) nickel plating is used to coat non-conductive substrates and geometrically complex parts — including printed circuit board (PCB) through-holes, valve bodies, and plastic housings — that cannot be uniformly plated by conventional electrodeposition. The bath is self-sustaining: a reducing agent (typically sodium hypophosphite or DMAB) reduces nickel ions to metallic nickel without an external current.

Nickel nitrate is used as the nickel source in certain electroless bath formulations, particularly where chloride-free chemistry is required to avoid corrosion of sensitive substrate materials. The low cobalt content (Co ≤ 0.01%) is especially important here: cobalt is a known catalyst poison that accelerates spontaneous bath decomposition, reducing bath life and increasing process cost.

Catalyst Applications

Supported Nickel Catalysts for Hydrogenation

Supported nickel catalysts are among the most widely used heterogeneous catalysts in the chemical industry, applied in edible oil hydrogenation, fine chemical synthesis, and petrochemical processing. They are typically prepared by wet impregnation: a porous support material (Al₂O₃, SiO₂, or activated carbon) is impregnated with an aqueous nickel salt solution, dried, and calcined to convert the nickel salt to nickel oxide, which is then reduced in hydrogen to give active metallic nickel.

Nickel nitrate is the preferred impregnation salt for several reasons. Upon calcination at 300–500 °C, the nitrate anion decomposes completely to nitrogen oxide gases (NO_x), leaving no residual anion in the catalyst. This is critical: sulfate residues from nickel sulfate poison nickel active sites; chloride residues from nickel chloride corrode reactor components and poison some catalyst formulations. The clean thermal decomposition of nickel nitrate ensures a high-surface-area NiO phase with minimal contamination, which translates to higher catalytic activity after reduction.

Steam Methane Reforming (SMR) Catalysts

Steam methane reforming — the dominant industrial process for hydrogen production — uses Ni/Al₂O₃ catalysts operating at 700–900 °C. Catalyst preparation via nickel nitrate impregnation produces well-dispersed nickel crystallites on the alumina support, which is essential for high reforming activity and resistance to carbon deposition (coking). Impurities such as Na and K (both ≤ 0.02% and 0.005% respectively in this grade) must be minimised in the precursor salt, as alkali metals at ppm levels promote sintering of the nickel phase at reforming temperatures, reducing catalyst lifetime.

Battery Cathode Precursor Synthesis

The rapid growth of lithium-ion battery production for electric vehicles and energy storage has created substantial demand for high-purity nickel salts as precursors for NMC (LiNi_xMn_yCo_zO₂) and NCA (LiNi_xCo_yAl_zO₂) cathode materials. In co-precipitation synthesis routes that require sulfate-free conditions, nickel nitrate provides the nickel component without introducing sulfate that would be incorporated into the cathode precursor hydroxide structure.

The extremely low Na content (0.00033% in COA) is particularly important for battery-grade applications, as sodium contamination in cathode materials increases cell impedance and reduces cycle life. Similarly, low Mg (0.0002%) and Ca (0.0001%) prevent unwanted substitution in the layered oxide lattice.

Purity Requirements: Why Grade Matters

Not all nickel nitrate is equal. Industrial-grade material may contain significantly higher levels of metallic impurities than the electroplating and catalyst specifications demand. The table below illustrates the critical impurity thresholds for each application sector:

This grade meets or significantly exceeds the requirements of both application sectors, making it suitable for demanding electroplating operations and high-performance catalyst synthesis without further purification.

Frequently Asked Questions

What is the CAS number for nickel nitrate hexahydrate?

The CAS number for nickel nitrate hexahydrate is 13478-00-7. The anhydrous form has a separate CAS number (13138-45-9), but the hexahydrate is the standard commercial form.

Why is nickel nitrate preferred over nickel sulfate for catalyst preparation?

Because the nitrate anion decomposes cleanly to gas (NO_x) during calcination, leaving no residual anion in the catalyst. Sulfate residues from nickel sulfate can poison active sites and remain in the catalyst up to 600 °C or higher, reducing catalytic activity.

Does Unifarm supply COA and MSDS for nickel nitrate?

Yes. Full batch COA (14 parameters including all major metallic impurities) and SDS/MSDS are provided with every shipment. Contact our team for sample documentation before placing a trial order.