Introduction

Traditional plating, also known as “electroplating,” is the process of reducing metal ions to their metallic state and depositing them as such at the cathode using electrical energy. Electroless plating is a chemical reduction method that involves catalytic reduction of a metallic ion in an aqueous solution containing a reducing agent and subsequent metal deposition without using electrical energy. A completely new stabiliser method is used in contemporary electroless nickel plating.

It’s made to be cost-effective and straightforward to use. This innovative method brightens dull metals and produces thicknesses of 100 mm or more without pitting or roughness. Even at a temperature of 95 °C, the bath components do not break. The electroless Nickel plating coating has been widely utilised on machining and finishing equipment to increase the life of moulds, plastic extruders, pumps, and valves subjected to harsh service conditions.

Furthermore, electroless plating (ELP) has been regarded as a promising metallisation process due to its ease of use (no complex and expensive equipment is required, as with vacuum-based vapour deposition methods) and the uniform coatings that result, even on non-conductive and complexly shaped surfaces.

electroless nickel plating

electroless nickel plating

Benefits of electroless nickel plating 

Because electroless plating is a chemical reduction process, the resulting coatings are consistent in thickness across the plated item. Because the coating’s composition is similar throughout all layers, the deposit’s quality, particularly its physical and mechanical characteristics, is likewise consistent. The deposition rate can be as high as 20 to 25 mm/h when the solution composition, pH, and operating temperatures are appropriately chosen, fast enough for industrial applications.

Recent advancements in the electroless nickel method have resulted in exceptionally brilliant deposits similar to electroplated bright nickel while preserving the benefits of thickness homogeneity, which is particularly useful for parts or products with complicated geometry. In addition, the flexibility of electroless nickel deposits has increased significantly, allowing for easier post-plating processes like crimping and shaping. The drawback is that the ability to level is severely limited.

Properties of electroless nickel plating

Because of the outstanding characteristics of coatings, such as strong corrosion resistance, high wear resistance, good lubricity, high hardness, and acceptable ductility, the electroless deposition technique of Ni-P alloy coatings has become a well-known commercial procedure. Because of its application method and unique characteristics, hypophosphite reduced electroless nickel is a unique engineering material. The features of electroless nickel deposits are dramatically changed due to the presence of phosphorous/boron.

Ni-P coatings are homogeneous, rigid, and brittle when applied. A Ni-P coating that has been deposited can be used as a lubricant that is readily solderable and highly resistant to corrosion. With a few exceptions, the properties of deposits formed from borohydride or amino borane reduction baths are similar to those of electroless Ni-P alloys.

Ni-B deposits have high hardness, and these alloys may be heat treated to high temperatures, equivalent to or greater than hard chromium deposits. The Ni-B offers exceptional wear and abrasion resistance. However, these coatings are not fully amorphous, and their resistance to corrosive conditions is decreased. They’re also a lot more expensive than Ni-P coatings.

Applications of electroless nickel plating

Electroless nickel is typically utilised in technical applications that demand a consistent thickness, high hardness and wear resistance of the surface, and increased corrosion resistance. Thus,

(a) to deposit on complex shapes;

(b) to deposit on large surfaces, especially large interior surfaces;

(c) to deposit on surfaces subjected to wear;

(d) to replace expensive stainless steel vessels in some processing industries;

(e) to repair or salvage nickel-plated machine parts;

(f) to deposit nickel where electrical power is not available or possible;

(g) to improve enamel adhesion on steel.

For better corrosion resistance and homogeneity of deposition, the inner surfaces of pumps, driers, tubes, fuel containers and tanks, transport vehicles carrying various chemicals, storage tanks, valves, screws, nut fasteners, and other items are coated with electroless nickel. Electroless nickel is applied to cylinders for hydraulic pumps, piston rings, piston cylinders, cranks, bearing surfaces, rotating shafts, printing press components, motor blades, and other items to enhance wear and corrosion resistance lubrication circumstances.

Electroless nickel is applied to aluminium and aluminium components in aviation and spacecraft to increase wear and corrosion resistance. Electroless Ni also covers nuclear reactor components, light-alloy dies, radar waveguides, and printed circuit boards. It is used in the textile industry to produce a homogeneous, extremely wear-resistant, thermally conductive surface on rollers and crimpling tracks.

Electroless nickel is utilised in various industrial applications, including aerospace, automotive computers, electronics, food processing, hydraulics machinery, nuclear engineering, oil petrochemicals, plastics, power transmission, printing, pump valves, textiles, and so on.

Electroless nickel is increasingly recommended as a prelate for additives and semi-additive circuits because of its quicker build-up, higher solution stability, and consistent results. Electroless nickel has been utilised as a surface coating on wrought steel to prevent pressure build-up during lengthy storage. It has a minimal catalytic impact on hydrazine and methyl hydrazine breakdown.

Developments in electroless nickel plating

Because of its low capacity, non-magnetostriction, and low frictional resistance, permalloy films are appropriate for soft magnetic materials. In computer applications, they’ve been widely employed as magnetic recording head core materials. The effects of a tiny quantity of P or B on the magnetic characteristics of permalloy films were examined. It was discovered that raising the resistivity value enhanced the synthetic magnetic properties of the films. The impact of deposition factors such as pH and FeSO4/(FeSO4 1 NiSO4) mole ratios on the plating rate and deposit composition were investigated.

The inclusion of ferrous sulphate in the bath was discovered to impede the deposition of the alloy. As a result, the iron content of the deposits never reaches high levels. It was found that it was less than 15.62. Pct. For the first time in nanotechnology, electroless deposition enables photomasks and microdevices with nanosized adjacent components of varying thicknesses composed of diverse materials using a single optical photolithography technique.

These benefits significantly improve the device’s functioning capabilities and the elimination of unwanted gases and heat transfer. Other expensive and complex methods such as e-beam, X-ray lithography, or device manufacturing are considerably more beneficial and accessible than the proposed nanotechnologies. Photomasks with light phase shift Methods of manufacturing the ultrathin void-free and pore-free electroless coatings on micro-, meso- and nanosized particles (carbides, borides, \snitrides, oxides, diamond, graphite, etc.) are also presented. These techniques enable the creation of nanostructured composite materials and coatings with desired characteristics.

Conclusion

Electroless plating is a well-known surface modification technique that involves depositing a metal-metalloid alloy coating on various surfaces. Although electroless plating may be done on many metals (or alloys), electroless Ni-P coatings have gained popularity due to their high hardness, good resistance to wear, erosion, and rust.