Introduction

Nickel plating (Ni) is used for decoration and corrosion protection of steel, copper, aluminium and magnesium, for smoothing out surfaces, for black coatings, and for renewing worn machines components.
Mostly applied prior to chromium plating. Extremely tight tolerances for individual needs

Nickel electroplating is a technique of electroplating a thin layer of nickel onto a metal object. The nickel layer can be decorative, provide corrosion resistance, wear resistance, or used to build up worn or undersized parts for salvage purposes
Nickel electroplating is a process of depositing nickel on a metal part. Parts to be plated must be clean and free of dirt, corrosion, and defects before plating can begin. To clean and protect the part during the plating process a combination of heat treating, cleaning, masking, pickling, and etching may be used. Once the piece has been prepared it is immersed into an electrolyte solution and is used as the cathode. The nickel anode is dissolved into the electrolyte in form of nickel ions. The ions travel through the solution and deposit on the cathode

Nickel electroplating is a process of nickel deposition over a part immersed into an electrolyte solution and used as a cathode, when the nickel anode is being dissolved into the electrolyte in form of the nickel ions traveling through the solution and depositing on the cathode surface.
The nickel plating process is used extensively for decorative, engineering and electroforming purposes because the appearance and other properties of electrodeposited nickel can be varied over wide ranges by controlling the composition and the operating parameters of the plating solution.

Decorative applications account for about 80% of the nickel consumed in plating; 20% is consumed for engineering and electroforming purposes. Autocatalytic (electroless) nickel plating processes are commercially important, but are outside the scope of this article. The annual worldwide consumption of nickel for electroplating, including nickel consumed as plating salts, is approximately 180 million pounds (81,700 metric ton s), and accounts for 11 to 12 percent of world nickel consumption.

Nickel is also used for engineering purposes. Its deposit offers more wearability than softer metals such as copper, brass and zinc and can be used when wear resistance is needed, such as on molds. And since nickel can be made to plate with little or no stress it is used for electroforming.
Metallic-coated steel NICOR and HILUMIN are designed to make further processing more efficient and cost-effective. Not only this, they also give you semi-finished, electro nickel-plated end product of superior quality. Cold rolling, electroplating with nickel and diffusion annealing provide excellent deep drawing capability and superb corrosion resistance. NICOR and HILUMIN are used in many different applications in market sectors including:
• Battery Production • Electronics • Automotive • Telecommunications • Computers • Office Equipment

Corrosion Performance

The improved performance of multilayer nickel coatings is due to the combination of layers of nickel having different electrochemical reactivities. If one measures the corrosion potentials of various nickel deposits in the same electrolyte, one finds that the bright nickel Deposits display more active dissolution potentials than do the semi-bright nickels. If bright and semi-bright nickel deposits (for example, in the form of foils separated from the substrate) are electrically connected in the electrolyte, electrons will flow from the bright nickel to the semi -bright nickel. The result is that the rate of corrosion of the bright nickel is increased, whereas the rate of corrosion of the semi -bright nickel is decreased. In a composite coating consisting of bright nickel over semi -bright nickel, this is manifested by enhanced lateral corrosion of the bright nickel layer and delayed penetration of the semibright nickel layer. The extent to which bright nickel protects the underlying semibright nickel layer by sacrificial action is dependent on the difference between the corrosion potentials of the semi – bright and bright nickel. The difference should be at least 100 millivolts (as measured by the STEP Test described below), and there is evidence that larger differen ces in potential are beneficial, especially in low current density areas of complicated parts. If the difference becomes too great, appearance suffers because of the accelerated corrosion of the bright nickel layer; that is, there is an optimum value that represents a compromise between preventing basis metal attack and controlling superficial corrosion. The result is that penetration of the coating and exposure of the underlying substrate occur slowly. Multilayer nickel coatings are, thus, more protective than single – layer bright nickel coatings of equal thickness.

Two coating weights are commonly used to meet the automobile industryÂ’s requirements :
Grade A : coating weight > 24 g/m², average thickness 5 to 7 µm
Grade B : coating weight > 36 g/m², average thickness 8 to 10 µm
Greater coating weights may be applied to increase the duration of the corrosion protection

Nickel Alloy Plating and Composites

Although discussion of alloy plating is beyond the scope of this article, nickel alloy plating processes of commercial importance include nickel-iron (without brighteners), nickel-cobalt, nickel -palladium and tin-nickel. An alloy plating process that is growing in importance is zinc-nickel containing 8 to 12 per cent nickel. In addition, the incorporation of inert particles within a nickel matrix is possible and coatings that incorporate silicon carbide, diamonds, mica, PTFE and other materials are being applied for engineering purposes

Controlling pH, Temperature, Current Density and Water Quality

The pH of the nickel plating solution will rise during normal operation of the bath necessitating regular additions of acid to maintain the pH within the prescribed limits. (A decrease in pH accompanied by a decrease in nickel ion concentration indicates the process is not functioning properly.) The operating temperature may have a significant effect on the properties of the deposits and should be maintained within specified limits (plus or minus 20 C) of the recommended value. In general, most commercial nickel plating baths are operated between 38 to 60 0 C (100 to 140 0F).The nickel plating process should be operated at specified current densities by estimating the surface area of the parts and calculating the total current required . The practice of operating theprocess at a fixed voltage is not commended. Controlling cathode current density is essential for accurately predicting average nickel thickness, for achieving uniform coating thickness on complicated shapes, and for producing deposits with consistent and predictable properties. Since current density determines the rate of deposition, it must be as uniform as possible to achieve uniformly thick nickel deposits. The nickel plating solution has an electrical resistance and almost all components to be plated have prominent surfaces that are nearer the anode than recessed areas. The current density is greater at the prominences because the anode-to -cathode distance is shorter and therefore has less electrical resistance. The apportioning of the current in this way is called “current distribution”. This means that the recessed areas receive a thinner nickel deposit than the prominent ones. Current distribution is controlled by proper rack design and proper placement of components on those racks; by the use of nonconducting shields and baffles; and by the use of auxiliary anodes, when necessary. With care, relatively good thickness distribution can be achieved. The quality of the water used in making up the bath and in replacing water lost by evaporation is important. Demineralized water should be used, especially if the local tap water has a high calcium content (greater than 200 ppm). Filtering the water before it is added to the plating tank is a useful precaution to eliminate particles that can cause rough deposits

Engineering Purposes

Electroless nickel plating intended for engineering purposes is used for wear resistance, abrasion resistance and such corrosion protection of parts as the specified thickness of the nickel plating provides. Heavy deposits of the electroless nickel plating may be used for build up of worn or undersized parts, or for salvage purposes, and to provide protection against corrosive chemical environments.

Watts Nickel per QQ-N-290A – Nickel plating

Watts nickel is an electrolytic system that, as a component of our SuperBright ™ process, provides very bright, decorative finishes. Watts nickel also provides corrosion resistance according to thickness, good abrasion resistance, and a low coefficient of thermal expansion. Watts nickel has a relatively low tensile strength and hardness and relatively high internal stress and therefor is not recommended in engineering applications where part deformation or flexure may occur.

Electroless Nickel plating – Electroless Nickel Per Mil-C-26074

(Medium & High Phosphorus Content)

Professional Plating provides both mid-phos and high-phos electroless nickel plating (EN). Electroless systems are applied to the surface of base metals by a chemical reaction mechanism that does not require electrical current. The benefit of this process is that electrical flux density fields do not govern metal deposition thickness. Flux fields tend to be non-uniform and therefore can result in non-uniform thickness of the electrodeposits. Electroless systems have superior hole filling and leveling characteristics, which make them ideal as a first layer for almost all other electroplated, finishes. Depending of thickness and phosphorous content, electroless nickel plating is an excellent corrosion inhibitor. High-phos electroless nickel plating system specifications were developed by the NATO as a result of their experience with aggressive corrosion conditions. Electroless nickel plating systems have hardness and internal stress levels at the mid-range of all nickel systems and therefore should be specified carefully when subsequent part deformation or flexure will occur.

Sulfamate Nickel Plating

Sulfamate nickel provides the lowest hardness, lowest internal stress and highest ductility of all the nickel plating systems. The finish is dull; this is an engineering finish and not a decorative finish. Sulfamate nickel has excellent solderability good corrosion resistance. The high ductility of sulfamate nickel makes this product an excellent candidate for applications where part flexure or deformation, such as crimping, will occur.

Matte Sulfamate Nickel plating produces a 99.9% pure deposit without any organic brighteners or levelers. The high purity of the deposit affords temperature resistance up to the 1400°C+ melting point of pure nickel. These deposits have a full matte appearance with a slight yellow or golden cast not known for decorative appeal. They also have extremely low deposit stress that can be in the compressive range. The low stress of sulfamate nickel plating yields nickel deposits with ductility, elongation and machinability far superior to other nickel deposits.
Matte Sulfamate Nickel plating excels in joining applications including brazing, soldering, over molding, epoxy bonding, and welding. The high purity and lack of co-deposited organics improves the wetting of the nickel deposit when soldering and makes sulfamate nickel plating the preferred underplate and diffusion barrier when tin plating, silver plating or gold plating for solderability or brazing. In addition, the unleveled matte surface makes sulfamate nickel plating the choice for adhesion in over-molding or epoxy bonding applications.
Semi-Bright Sulfamate Nickel plate is used in places where a bright surface gives a decorative appearance. Semi-Bright Sulfamate is primarily used in areas where handling would discolor Matte Sulfamate nickel. Semi-Bright sulfamate nickel has excellent corrosion resistance and slightly lower solderability than Matte Sulfamate nickel. However, it is harder and has excellent corrosion resistance.
Coastline Metal Finishing has extensive experience in Sulfamate Nickel Plating in uses extending from shuttle turbo-pumps to photo machined sheet stock.
Bright Nickel plating is often used as an undercoating to improve reflectivity and leveling to smooth out surface defects. Bright Nickel plate also provides an excellent barrier coating to reduce porosity and improve corrosion resistance. If an article is to be flexed, bent or distorted in the application, Sulfamate Nickel should be considered.

Nickel Plating for Corrosion Protection

Nickel Plating has the ability to offer outstanding corrosion protection, especially when subjected to high temperatures. It is used extensively in automotive under bonnet applications where its temperature and corrosion resistance are vital.

Benefits of nickel plating

  • Nickel offers corrosion protection
  • Nickel is wear resistant
  • Nickel provides a good barrier between base material and precious metals
  • Nickel aids in mitigating the growth of tin whiskers