We have put together a little helpful guide for you with some useful information.
Zinc plating is a process where zinc is applied by using a current of electricity. While it does provide some rust protection, its thinner coating is not as rust resistant as hot dip galvanising. It´s main advantage is that it is cheaper and easier to weld.
Galvanisation is when a protective zinc coating is applied to steel or iron, to prevent rusting.
The most common method is hot-dip galvanising. This is when metal parts are fully submerged in a bath of molten zinc.
Be careful when choosing your product! The fact that it says ‘galvanised’ doesn’t mean it’s ‘hot dip galvanised’. Electro-galvanising is another term for zinc plating. So when you see ‘galvanised’ use your newly acquired knowledge to make sure it is hot dip galvanised and not electro-galvanised.
Hot dip galvanising or zinc plating can be used on anything from small nuts and bolts to large beams for buildings. The steel is put in a big bath, where the coating is applied.
If it’s galvanised, it will be dull grey and a little rough. A zinc plated product will be shiny and smooth. A hot dip galvanised product has the best protection against rust, even though it’s a bit ugly.
Whether the steel is to be hot dip galvanised or zinc plated it is prepared in a similar way. The steel is cleaned to remove all oils, paint, grease, mill scale (small flakes of metal) and rust in a bath of acid.
Steel, when being hot dip galvanised is dipped into a 450°C bath of molten liquid zinc. The steel and the liquid zinc bond together because of the high temperature. The steel and the zinc become one.
Zinc plating, on the other hand, is immersed in a cold chemical solution of zinc and uses an electrical current to apply a layer of zinc.
The thickness of the coating is measured in microns or micrometre’s (μm). Zinc plating usually requires a minimum thickness of 5μm (.005mm) and a maximum of 25μm (.025mm). It would become too technical and expensive to coat the steel any thicker than this.
Hot dip galvanising usually requires a minimum thickness of 45μm (.045mm) and goes beyond 100μm (.1mm)
Nickel plating can add durability, hardness, conductivity, and heat-resistance to your product, in addition to protecting against corrosion and enhancing its aesthetic appeal. But before you enlist plating services from a metal finisher, you must first decide between two plating methods: electrolytic or electroless plating.
The following guide explains both processes, how they differ, and their distinct advantages.
What Are Electrolytic and Electroless Nickel Plating?
Traditional electrolytic nickel plating requires a catalyst and a direct current (DC) charge to start a chemical chain reaction to coat an object (the substrate) with a thin layer of nickel.
However, with electroless nickel plating, no catalyst or charge is needed. Instead, electroless formulas include a chemical reducing agent (phosphorous) that allows the user to coat the substrate without further processing.
Both methods add a thin layer of nickel to the target surface, but electroless nickel plating (ENP) provides additional wear- and corrosion-resistance, lubricity, and ancillary performance characteristics compared to its electrolytic counterpart. Also known as autocatalytic coating, ENP can be used on projects with tight tolerance specifications and is easy to apply in uniform layers.
Electrolytic nickel plating, on the other hand, is typically thicker around the substrate corners and edges and can’t deliver the same level of precision. During electrolytic plating, deposit density is controlled by the length of time the product is submerged and how many amps per square foot are applied.
Process of Nickel Plating
First, the substrate material must be cleaned and pretreated before it can be plated with nickel. Pretreatments vary depending on the substrate type and the product’s intended use.
Next, the product is placed into a plating bath, which consists of positively charged, dissolved nickel phosphorus. The substrate automatically draws the positively charged nickel ions onto its surface, completing a fine layer of coating. Electroless nickel plating does not require electricity, nor does it need constant filtration to keep debris from adhering to the surface.
Electroless nickel plating is common among these industries:
Electrolytic Plating Process
Just like with electroless nickel plating, electrolytic plating also begins with cleaning and pretreating the substrate. Next, the product is placed into a bath with a conductive base and positively charged nickel. Once the object is submerged, an external electrical current or rectifier is administered to the solution. Electricity charges the nickel anodes, causing them to release ions that attach to the surface of the substrate, thereby completing the plating process.
Advantages to Electrolytic Plating
Some situations are better suited to electrolytic plating instead of electroless nickel plating. Here are a few benefits of electrolytic plating:
Choosing the right electroplating method is essential for achieving optimal results and minimizing the risk of damage to the finished product. Two of the most commonly applied processes for plating multiple workpieces are barrel and rack plating. Each offers several advantages, as well as points the plater and customer must consider when determining the most appropriate method for their project.
As the name implies, barrel plating entails placing the parts inside a barrel typically constructed of polypropylene. The barrel contains center bars that conduct the electrical current. The barrel rotates slowly while immersed in the electrolytic plating solution. This causes the parts to tumble or “cascade,” which provides an even, uniform coating application. Typical barrel plating applications include enhancing corrosion protection, increasing aesthetic appeal and producing an engineering finish that protects the parts against wear and tear.
Barrel plating offers a cost-effective means of plating a high volume of small, durable parts such as stampings and fasteners. It also works well for plating parts of various shapes and sizes. Barrel plating requires a smaller investment in equipment and is less labor-intensive than rack plating, which ultimately results in a lower process cost to the customer. On the downside, most barrel plating techniques require a low electrical current, which can increase the time that the parts are exposed to the plating solution.
Rack plating differs from barrel plating in that the parts are affixed to metal racks with screws, wires or spring fingers. This causes the parts to remain stationary upon immersion of the metal rack into the plating solution. Consequently, metal platers prefer rack plating for delicate parts that might not be able to withstand the tumbling or cascading action produced by barrel plating. Rack plating also works well for large or complex components.
In addition to affording increased protection against damage to parts, the rack process can plate contours and intricate shapes more efficiently. Rack plating is the preferred choice in industries where a high-quality finish is paramount such as military and defense, automotive, medical and electronics. Disadvantages of rack plating include the higher cost and increased labor requirements. In many cases, it may be necessary to design and manufacture a customized rack for specialized applications.
Both barrel and rack plating are compatible with a wide variety of metal finishing technologies such as zinc, tin, copper and nickel, as well as precious metals such as gold and silver.
The chrome plating process has many applications in the manufacturing, production and consumer goods industries. Commonly known as just "chrome," chrome plating provides a protective coating and shiny luster when applied to metal parts and products. Chrome plating can have decorative purposes or can enhance the desirable properties of machine components. You can achieve these two goals with different types of chrome plating — decorative chrome plating and hard chrome plating.
Which Plating Method Is Right for You?
Decorative chrome plating offers exceptional aesthetic appeal, while hard chrome plating provides superior strength and hardness, low friction and lasting durability. Both types of chrome plating are useful for different applications, and the best plating method for you will depend on your unique project needs. For consumer goods, decorative chrome plating can provide the necessary protection and desired appearance, while hard chrome plating is better-suited for high-stress industrial applications.
The Difference Between Hard Chrome and Decorative Chrome Finishes
The primary difference between decorative chrome and hard chrome plating is the thickness of the chrome plating on the final product. Decorative chrome plating is thinner than hard chrome and is primarily for aesthetic appeal and as a protective coating.
You might hear people call decorative chrome plating nickel-chrome plating, as it gets applied over nickel plating, rather than directly to the metal substrate. In some applications, copper plating also gets first to improve the strength of the final product. Decorative chrome plating is very thin compared to more durable hard chrome plating, typically measuring just a few microns.
Hard chrome plating is thicker than decorative chrome finishes and is useful in many industrial applications for its strength, wear resistance, corrosion resistance and other beneficial properties.
Decorative chrome and hard chrome plating result from the same chrome manufacturing process but differ in their final properties and common applications. Chrome plating uses an electrolytic process that applies chromium plating to a metal component in an electrolytic bath at a rate of about 25to 30 microns per hour. The substrate first gets cleaned thoroughly and, if necessary, treated with chemicals to improve the adhesion of the plating. The component then goes into a chrome plating vat for chrome dipping, where an electric current deposits chromium onto the substrate.
The electrolytic process and chrome dipping apply both types of chrome plating evenly to components of unusual shapes, sizes and textures. Hard and decorative chrome plating can adhere effectively to ridged or flat surfaces, in small holes or recesses and to cylindrical parts. With a large enough plating vat, you can apply chrome plating to metal components of nearly any size. The versatility of chrome plating makes it a popular chrome finishing choice for a wide range of applications in manufacturing and consumer goods.
Hard chrome plating can benefit nearly any machine component or part. Because of its low friction, hard chrome plating is effective for moving parts like rotors and pistons to reduce operating temperatures and improve the lifespan of equipment parts. Manufacturers of hard chrome plating can polish it to superior smoothness for rounded components like print cylinders and rollers, while still providing exceptional resistance to wear when used with abrasive products like textiles, paper, limestone or sand.
Decorative chrome plating has more limited applications than hard chrome plating, but serves an essential role in many industries. Although it does not offer the same strength and durability as hard chrome, decorative chrome finishes can still provide a thin protective coating when applied to automobile parts, tools and utensils. Decorative chrome finishes protects against rust and wear when products get exposed to wet or corrosive conditions. This protection can be further extended by the application of a copper base layer below the nickel.
Decorative chrome plating also provides a smooth and shiny appearance that is easy to clean, making it desirable for various consumer products. If used solely for aesthetic appeal, decorative chrome plating is sometimes applied using inexpensive imitation chrome finishes instead of actual chromium. Here are a few common applications of decorative chrome plating.
Decorative chrome plating is primarily an aesthetic feature, though it also protects against corrosion and wear. However, because decorative chrome is so thin, it does not offer as much durability as hard chrome plating. If you find yourself asking, "How long does decorative chrome plating last?" you should be aware that it can wear off over time. Here are the primary benefits of decorative chrome plating.
For applications where aesthetics and function are essential, decorative chrome plating can work well. Attractive and corrosion-resistant decorative chrome can enhance many consumer goods.