Electroless Nickel Plating is also known as ENP. Its is a chemical process which deposit Nickel Phosphorous layer on the components without of the use of electric current during the process. The major advantage of this process is that it provide even surface coating across the bath on all the components. So there is no uneven coating issue from one component to another component. Also the chemistry has proven the hardness achieved in the coating thickness is minimum 350 Hv to 1000 Hv(based on the base alloy)
The Electroless Nickel process has several advantages over Electrolytic electroplating:
- Virtually unlimited throwing power
- Little or no excess deposit at high points
- Deposits of excellent physical and chemical properties
- Reduced hydrogen charging (hydrogen embrittlement)
- Ability to coat surfaces which would be difficult or impossible by electroplating.
The principal disadvantage of the electroless process is high cost.
Electroless nickel is sometimes an economical treatment to improve the performance of carbon steel in mildly corrosive environments (such as chlorides, trace acids, caustic solutions) and in situations where light wear may occur in service. It is, however, difficult to deposit electroless nickel on chromium-containing steels. Electroless nickel can be deposited on the internal diameter of tubular components and other difficult to access surfaces.
There are variants of electroless nickel plating, the most common of which include:
- composite electroless nickel, in which SiC (silicon carbide) particles are co-deposited with the nickel to enhance its strength and wear resistance.
2. duplex electroless nickel where an undercoat containing 14% phosphorus is used with a top coat of 5% phosphorus.
Metal Polishing: There’s no finish like a mirror finish. But what’s the best way to take those old valve covers from scuffed up to super shiny? If you want to get into polishing metal, you need a little know-how and the right tools and supplies.
Prep Work: With raw extruded or cast metals such as aluminum and stainless steel, sanding can be a key first step towards achieving a mirror-like finish. If you’re working with relatively smooth metal, you probably won’t need to sand. Remember, sanding will never make it shinier, but it can save you time and make the surface flatter.
Wet Sanding: For hand sanding flat surfaces, wet sandpaper can be effective. Assess the casting lines or scratches and determine the grit of sandpaper to start with. Generally if you can feel the scratch lines, use a 320 grit sandpaper. Make good use of your time: Start with a coarser grit and from there work your way up to 1,500-2,000 grit in 200-grit increments. This will drastically reduce your polishing time and produce a finish that’ll please the pickiest of people. You can find wet sandpaper in a variety of grits here. Try to keep your paper wet to avoid clogs. This is especially important when polishing aluminum.
Sanding with a Die Grinder: Another option for surface prep—one with a little more zing than wet sanding—is a die grinder. Because die grinders work with a variety sanding attachments such as roll-on surface prep discs, mounted flap wheels, sanding discs and more, you can find the abrasiveness and shape you need to fit your workpiece.
You can also use your die grinder for polishing, especially for curved surfaces, like intake manifolds. We have a great selection of shaped buffs, mini polishing wheels and mandrels, as well as polishing kits with everything you need, including polishing compound.
Polishing and Buffing Wheels: Choosing the correct buff is an important step in achieving your desired outcome. For steel and stainless steel, start with a full-sewn or spiral-sewn wheel and an aggressive cutting compound, such as a grey cutting compound. This will quickly diminish light scratches and surface imperfections.
Laser marking, In simplest terms, laser marking is a permanent process that uses a beam of concentrated light to create a lasting mark on a surface. Typically performed with a fiber, pulsed, or continuous wave laser machine, laser marking encompasses a wide variety of applications. The most common types of laser marking applications are annealing, carbon migration, discoloration, engraving, and etching.
Laser marking can be automated and processed at high speeds, while leaving permanent traceability marks on a range of materials, including steel, titanium, aluminum, copper, ceramic, plastic, glass, wood, paper, and cardboard. Parts and products can be marked with text (including serial numbers and part numbers); machine-readable data (such as barcodes, Unique ID codes, and 2D Data Matrix codes); or graphics.
Laser marking works by using a focused beam of light to mark the surface of a material. When the beam interacts with the material’s surface, it alters the material’s properties and appearance. This concentrated beam targets only a specified area, allowing the laser marking machine to create precise, high quality, high-contrast marks that are easy to read or scan on virtually any surface. This feature makes laser marking ideal for applications where accuracy and permanency are critical to success.
Properties of Electroless Nickel
It is the superior properties of electroless nickel coatings that caused the rapid expansion of its use. No other coating has the combination of properties offered by electroless nickel.
Corrosion Resistance and Corrosion Protection
One of the most common reasons for the use of electroless nickel coatings in functional applications is its excellent corrosion resistance. In the very corrosive conditions encountered in drilling and producing oil wells, for example, electroless nickel has shown its ability to withstand the combination of corrosive chemicals and abrasion.
The alloy content of the EN deposit influences its performance in most environments. Phosphorus alloys typically provide better protection than boron reduced coatings. In hot, highly alkaline solutions, low phosphorus deposits are more corrosion resistant than high phosphorus alloys. However, in most other chemical environments, high phosphorus alloys provide superior corrosion resistance.
The density of EN coatings declines with increasing phosphorus content. An electroless nickel deposit containing 3 percent phosphorus has a density of 8.5 g/cm3 , while that of a deposit with 11 percent phosphorus has a density of 7.75 g/cm3 . These values are lower than those of pure metallurgical nickel (8.91 g/cm3 ).
Coefficient of Thermal Expansion
The coefficient of thermal expansion of a deposit containing 8 to 9 percent phosphorus is about 13 x 10-6 /°C. This compares to values for electrodeposited nickel of 14 to 17 x 10-6 /°C. Thermal Conductivity The thermal conductivity of an electroless nickel deposit containing 8 to 9 percent phosphorus is 0.0105 to 0.0135 cal/cm/sec/°C. Electrodeposited nickel has a value of 0.19 to 0.26 cal/cm/sec/°C.
The final melting temperatures of electroless nickel deposits vary widely, depending upon the amount of phosphorus alloyed in the deposit. The initial melting point is about 1630 °F (890 °C) for all deposits. This temperature corresponds to the eutectic point for nickel phosphorus.
Electroless nickel deposits containing greater than 8 percent phosphorus are considered to be essentially nonmagnetic as plated. The coercivity of 8.6 percent and 7.0 percent phosphorus content deposits has been reported at 1.4 oersteds and 2.0 oersteds respectively. A 3.5 percent phosphorus content deposit produces a magnetic coating of 30 oersteds. When the phosphorus content is increased to 11 percent, the deposit is completely nonmagnetic.
Coating thickness measurements with devices that rely on the nonmagnetic characteristic of the coating become inaccurate if phosphorus content is below 9 percent.
Heat treatment of electroless nickel at temperatures over about 520 °F (270 °C) will increase the magnetism of the deposit. Even deposits that are completely non-magnetic as plated, will become highly magnetic when heat-treated above 625 °F (330 °C). At these temperatures amorphous solid solutions of phosphorus in nickel decompose to form nickel phosphide (Ni3P) and magnetic nickel.
The electrical resistivity of EN deposits also varies with their phosphorus content. Pure metallurgical nickel has a value of 6.05 microohm-cm. Electroless nickel deposits containing 6 to 7 percent phosphorus have resistivities between about 52 to 68 microohm-cm. The resistivity of a deposit containing 2.2 percent phosphorus is 30 microohm-cm, while that of a deposit with 13 percent phosphorus is 110 microohm-cm.
Heat treating electroless nickel reduces its electrical resistivity. Beginning at about 520° F (270 °C), heat treating decreases electrical resistivity due to the precipitation of nickel phosphide in the coating. The resistivity of an electroless nickel deposit with 7 percent phosphorus, heat treated to 1100 °F (600 °C), was reduced from 72 to 20 microohm-cm.
Electroless nickel-phosphorus alloys are easily soldered with a highly active acid flux. Soldering without a flux or with mildly active fluxes can be more difficult if the parts are allowed to form oxides by extended exposure to the atmosphere. The heat processing of electroless nickel plated parts can make soldering very difficult unless a highly active acid flux is used.
Welding of electroless nickel deposits is not commonly done. The dissolution of phosphorus in the weld can produce low melting point compounds and “hot cracks” and disintegration of the weld.
Excellent adhesion of electroless nickel deposits can be achieved on a wide range of substrates, including steel, aluminum, copper and copper alloys. Typical bond strengths reported for electroless nickel on iron and copper alloys range from 50 to 60,000 psi (340 to 410 MPa). The bond strength on light metals, such as aluminum, tends to be lower, in the range of 15 to 35,000 psi (100 to 240 Mpa).
Low temperature, heat treatment is commonly employed to improve adhesion of EN on all metals, particularly on light metals such as aluminum or titanium. During this heat treatment diffusion can occur between the atoms of the coating and the substrate.
The surface preparation and activation is one of the most important factors for producing excellent adhesion.
Electroless nickel can be deposited to produce a wide range of coating thicknesses, with uniformity and minimum variation from point to point. This uniformity can be maintained in plating both large and small parts and on components that are fairly complex, with recessed areas. Electroplating of such parts, on the other hand, would produce thickness variation and possible voids in the plating when coating holes and inside diameters. The range of thicknesses for electroless nickel in commercial applications is 0.1 to 5 mils (2.5 to 125 mm), although deposits as thick as 40 mils (1000 mm) have been reported. The typical plating rate of most baths is 0.3 to 0.8 mil/hr (7.5 to 20 mm/hr).