If you work with equipment with metal components, you know industrial plating is crucial for a wide range of metal machinery and parts. Plating is where a metal layer is applied to a component, and it offers a number of benefits that can increase equipment performance. It reduces wear and damage from corrosion, reduces friction and increases conductivity, among other things.

While understanding the importance of industrial plating may be fairly cut and dry, choosing the right kind of plating is more complicated. The intended use of the component to be plated determines the right kind of metal or process to choose because of the different attributes that various usages and environments require. Let’s compare two common types of metal plating — hard chrome plating and electroless nickel plating. The nickel plating vs chrome plating debate has been a hot topic in industrial communities, and we're going to highlight the advantages and disadvantages of each plating method.

We'll be covering both hard chrome plating and electroless nickel plating at length, but here are a few of the key differences between the two plating methods: Chrome plating is harder and more durable than nickel plating, while nickel plating is better for plating hard to reach areas and offers slightly better corrosion resistance. In terms of appearance, chrome plating provides a shiny and smooth exterior, while nickel plating creates a glossier surface with a yellowish hue.

Image: Chrome plating is the process of applying a layer of chromium to a metal object.

What Is Hard Chrome Plating?

Chrome plating is the process of applying a layer of chromium to a metal object. The first step in the industrial chrome plating process is typically degreasing and cleaning the surface the chromium will be applied to, which is known as the substrate. This component may also need other types of pre-treatment depending on its makeup. The plating professional will then lower it into in an electrochemical bath until the desired thickness is achieved.

Hard chrome, often called industrial chrome, differs from decorative chrome in that it is primarily designed to be functional rather than aesthetic. Decorative chrome’s main purpose is to enhance the visual appeal of an object by applying a thin chrome coating. Hard chrome plating is much more durable through a wide range of uses and environments.

What Is Hard Chrome Plating Used For?

At the end of the hard chrome plating process, you have a smooth coating that is functional and durable. Its attributes make it ideal for many different engineering applications.

The automotive industry uses industrial hard chrome plating frequently for parts that need to move while resisting wear such as pistons and shock absorbers. In the aerospace field, landing gear components have hard chrome plating.

Machine tools that encounter rough use are also often are plated with hard chrome. These items might include drills, extrusion screws, taps and dies.

In the manufacturing sector, chrome plating shows up on gears and plastic molds where it provides improved anti-stick and release capabilities.

Hard chrome can also be used to restore old and worn parts or to fix imperfections caused by mistakes during the manufacturing process.

Image: Electroless nickel plating is used for a wide variety of components in a range of industries, including the automotive, electronics and oil industries.

What Is Electroless Nickel Plating?

The electroless nickel plating process uses a nickel-phophorous alloy to coat a substrate. This protects it and improves its functionality. As the name suggests,  electroless nickel plating doesn’t require an electric current as hard chrome plating usually does. Instead, after the substrate is cleaned, pre-treated and activated, the nickel plating technique uses an autocatalytic chemical reaction to deposit the coating.

During the electroless nickel plating process, hypophosphite is used as a reducing agent, resulting in various amounts of phosphorous being present in the plating. Electroless nickel plating is categorized as having low, medium or high levels of phosphorous. Low phosphorous plating has approximately two to five percent phosphorous content. Medium has about six to nine percent, and high has around 10 to 13 percent. The most typical kind is medium plating with around eight percent phosphorus.

The amount of phosphorous in the plating can impact its attributes. Low phosphorus plating provides the hardest coating, medium is less hard but plates the fastest, and high phosphorus plating is the least hard but is the best for corrosion protection. All coatings can be baked to increase hardness, but this will reduce corrosion protection.

What Is Electroless Nickel Plating Used For?

Electroless nickel plating is used for a wide variety of components in a range of industries, including the automotive, electronics and oil industries.

Car manufacturers use it to protect parts, such as pistons, fuel injectors and cylinders, from wear and corrosion. The aerospace industry uses it for similar reasons on valves, engine shafts and other components.

The oil and gas industry uses electroless nickel plating for equipment that will face harsh conditions underground or underwater. It’s a critical part of various pumps and pipe fittings.

It’s also common to find nickel plating in electronics such as hard drives and printed circuit boards. Like hard chrome plating, it can be used in molds to improve release and anti-stick capabilities as well as to restore worn or damaged parts. It’s also a common plating used on packaging and handling machinery.

Substrate Surfaces

Chrome and electroless nickel plating both work well for a variety of substrate materials. Because the plating deposits onto all surfaces of the component uniformly in the plating vat, you can use both metals for irregularly shaped objects, including those with holes and recesses.

Although they can both cover uneven objects, electroless nickel will more quickly create a uniform coating. Chrome may need to be polished away in some places to create a more even covering. Electroless nickel plating also tends to result in a layer with a more constant thickness, meaning you often end up needing less nickel than you would chromium to plate an irregular object.

You can use chrome on many different kinds of metals, including stainless steel, copper, brass and more as well as on plastic. This makes chrome plating a versatile technique. Electroless nickel can be used on a variety of different metals and plastics as well.

Hardness Comparison

Hard chrome is, as the name implies, known for its hardness. This property helps it withstand the wear of industrial use including severe mechanical contact. As plated, it has a hardness of between 68 and 72 on the Rockwell C Scale.

Electroless nickel can also protect components from wear and tear that occurs over time, which helps parts to last longer and saves companies money on maintenance and replacement costs. This material has a hardness of 63 on the Rockwell C scale as plated.

If wear resistance is your priority, you may choose to go with hard chrome. Both chrome and electroless nickel, however, can protect your equipment and parts from wear.

Duration Comparison

Both hard chrome plating and electroless nickel plating tend to last a long time, even with consistent mechanical contact and other uses that might cause wear. Not only will plating protect the substrate, but using one of these long-lasting solutions will also save you money by cutting down on the frequency with which you need to plate your parts.

The electroless process is what gives the nickel in this plating application the durability that it has. Nickel applied with a conventional electrolytic method would tarnish over a relatively short period. Electroless nickel, however, lasts for a much longer time without degrading, making it a more economical choice.

Corrosion Resistance

One of the foremost benefits of metal plating, along with wear resistance, is corrosion resistance. Both hard chrome and electroless nickel can resist corrosion and protect the material from the degradation that would occur from coming into contact with its environment.

Although both plating materials offer suitable corrosion resistance, studies show that electroless nickel is superior in this area, especially in blind holes. These holes are more difficult to plate and tend to be more susceptible to corrosion. Electroless nickel plating creates a more even coat in these hard-to-reach places, making it more effective at preventing corrosion in these areas. While both are good choices, if corrosion resistance is your priority, you may want to go with electroless nickel.

Coefficient of Friction

The coefficient of friction refers to how easily one material can slide past another. It’s calculated by dividing the force needed to move the object along the other’s surface by the force that pushes them together. A low coefficient of friction means an object will slide easily, while a high one means the opposite. The coefficient depends on many factors, including the substrate being used, the thickness of the plating and environmental factors such as temperature.

Although calculating this number can be difficult, thanks to a number of tests in which these factors remained constant, we know that both hard chrome and electroless nickel have a lower static coefficient of friction than many other metals. Hard chrome, however, has a slightly lower coefficient than electroless nickel. It is also typically better at retaining oil, which makes movement easier. This makes hard chrome plating a popular choice for components that encounter a lot of friction like pistons, and hydraulic cylinders.

Chromium’s static coefficient of friction versus chromium is 0.41, while electroless nickel against electroless nickel has a coefficient of 0.45. So, hard chrome will likely slide better than electroless nickel, but the difference isn’t big enough to be a significant deciding factor when choosing between the two materials.

Conductivity

When the ability to conduct electrical current is one of the main attributes you’re looking for in a metal, people typically go for copper. Because copper conducts electricity so readily, the International Electrotechnical Commission created a standard for commercially pure annealed copper’s conductivity, known as the International Annealed Copper Standard (IACS). To describe the conductivity of a metal, you can express it as a percentage of the IACS.

Copper on this scale is 100 percent. Chromium is 13 percent, so it has 13 percent of the conductivity of copper. For comparison, gold is around 73 percent, pure silver is around 105 percent. Hard chrome and electroless nickel plating aren’t typically used for their electrical conductivity attributes. They are conductive, but not as much as some other metals.

Appearance

Although appearance is not usually the primary concern in industrial uses, it’s an added benefit of choosing either hard chrome plating or electroless nickel plating. Chrome provides a shiny, smooth and modern look. Its style is part of what made it so popular.

The color of nickel is another classic look that you can see in the majority of fixtures in most homes. Electroless nickel plating offers a glossier appearance than electrolytic plating, and unlike more conventional nickel, electroless plating’s yellowish hue fades over time.

What to Consider and How to Choose

When it comes time to choose between hard chrome plating and electroless nickel plating, you might be faced with a difficult decision. Both are useful, but the right option for you depends on how you plan to use the plated component. Here’s what you should consider when weighing your options.

Wear: Will the use of the component cause it to wear down over time? The likelihood of a part wearing out is influenced by how often it’s used and the other objects it comes into contact with.

Environment: What kind of conditions will you use the component in? Consider whether it will be exposed to moisture, excessive heat or cold and other environmental factors.

Motion: Is the component a moving part that needs to run smoothly without wearing down? A part that gets stuck can slow down or halt processes and damage equipment.

Shape of the substrate: Is the shape of the item to be plated relatively smooth and uniform, or is it irregular? Check for holes, indentations, abnormally-shaped parts and rough surfaces.

Why Choose Hard Chrome Plating?

Once you’ve analyzed your needs for your plated component, you can determine whether hard chrome plating is the right choice for you. It has the following attributes:

Superior Hardness: If you need your plating to be exceptionally hard and durable, go with hard chrome. For components that face the potential for a lot of wear, hard chrome is the best choice for a component that will function well even in harsh conditions and last for a long time.

Lower Coefficient of Friction: If the component you are plating is a moving part, opt for hard chrome. It has a low coefficient of friction, which means it’s easier for things to move along it. It also retains oil well, which improves performance.

Conductivity: If you’re looking for the more conductive of the two, the winner is hard chrome. While it can conduct electricity, it is, of course, not nearly as conductive as metals like copper and gold.

Why Choose Electroless Nickel Plating?

Hard chrome is a versatile and highly-functional plating material. In some situations, however, electroless nickel would be the better choice. Here’s when you should go for electroless nickel:

Exceptional Corrosion Resistance: If corrosion is a major concern of yours, electroless nickel should be your go-to plating material. The uniformity and smoothness of the plating leaves no room for moisture and other elements to get through, protecting your component, helping it to work better and last longer.

Uniformity: Electroless nickel’s uniformity enhances its corrosion resistance and also makes it perfect for coating irregularly-shaped items. If the component has a lot of rough surfaces, holes and other hard-to-cover areas, reach for this material to make sure every inch of your equipment gets protection.

Plating

Oftentimes, you might find yourself in situations where you want both capabilities that hard chrome is better at and ones where electroless nickel has the edge.

The good news is that both materials are excellent in many of the same areas, even if one is somewhat better than the other. They’re both resistant to wear and corrosion, support motion, can be used on irregularly-shaped objects and conduct electricity. Either way, you get a high-quality plating material. For this reason, you might sometimes see components with plating that combines chrome and electroless nickel.

(Hard Chrome Plating)