A process referred to as zinc plating is usually used to protect metals like iron and steel against the relentless forces of corrosion. Zinc plating involves the electrodeposition of a thin coating of zinc metal onto the surface of another metal object, called a substrate. The zinc coating creates a physical barrier that forestalls rust from reaching the underlying metal surface. Zinc is chosen due to its innate ability to fight corrosion. In fact, zinc is usually said because the corrosion-prevention workhorse.
Plating with zinc may be a relatively recent process, and it failed to gain widespread use until approximately 1980. before that time, cadmium was the popular metal for electroplating in applications where maximum protection against corrosion was required. However, cadmium is a highly toxic substance which will have a cumulative poisoning effect over an extended period of the time.
While zinc cannot quite match cadmium in terms of its anti-corrosion capabilities, it’s viewed as a more bio-friendly alternative. lately, the utilization of cadmium plating is mostly restricted to applications where plating with zinc won’t provide sufficient corrosion protection or additional levels of protection are required. However, the utilization of cadmium in plating operations must suits current environmental regulations.
Zinc plating Process
Zinc plating is a complex process that needs a high level of experience. Specialized equipment and machinery are also required, including a rectifier, plating station, ancillary tank for correct dissolution of the zinc anode, and a reservoir. Here’s a summary of how a typical zinc plating process works:
- Preparing and cleaning the surface — It’s essential to thoroughly clean the surface of the substrate before plating. Any debris or contaminants remaining on the surface will prevent proper adhesion of the zinc coating. An alkaline detergent solution is often used for surface cleaning, which is followed by the appliance of an acid treatment to get rid of surface rust. This latter procedure is named as pickling.
- Preparing the plating solution — Zinc plating requires the immersion of the substrate into a specially formulated electrolyte solution, which is mentioned because of the plating bath. the bath consists of the zinc metal ionic solution and various chemicals that facilitate plating processes. They also help produce the specified chemical and physical properties of the finished product.
- Choosing the suitable zinc plating procedure — After solution preparation, the parts are ready for plating. The chosen method could involve rack plating, where larger parts are affixed to metal racks which are placed inside the tank containing the plating bath. The parts remain stationary during plating. Barrel plating is generally used for smaller parts — rather than a plating tank, the parts are placed inside a barrel and rotated, which provides a more uniform finish.
- Introducing the electrical current — Electroplating is also referred to as electrodeposition because an electrical current is used to deposit metal ions onto the surface of the substrate. in the case of zinc plating, the substrate is the cathode. A DC current originating at the anode is introduced into the bath and flows to the substrate. The zinc ions are then deposited onto the surface. the present flows from the cathode back to the anode to finish the circuit.
- Post-treatment procedure — Upon completion of the electrodeposition process, the parts are ready for post-treatment. This normally involves rinsing the parts in water to get rid of any remaining contaminants and plating bath remnants. In cases of heavy contamination, the parts may have to be rinsed several times. the final step is to thoroughly dry the zinc-plated parts. In situations where additional corrosion protection is required, the appliance of passivates and sealers are often included within the post-treatment process.
Benefits of Zinc Plating
Zinc coating offers quite excellent protection against corrosion. Other key reasons to decide on zinc plating include:
- Low cost — Because zinc are often found in abundance, it’s viewed as a less expensive plating process than when using precious metals like gold or palladium. This makes zinc plating a preferred choice for any company that is keeping an in depth eye on expenditures.
- Increased strength — Although zinc may be a relatively lightweight metal, a zinc coating can increase the strength of the substrate.
- Low-stress deposit — Applying a zinc coating won’t place an undue amount of stress on a metal part or component.
- Flexibility — Zinc is compatible to be used in an exceedingly wide selection of bath chemistries, providing greater flexibility for customizing the plating outcome. Zinc is additionally amenable to both rack and barrel plating processes.
- Ductility — Zinc is a particularly ductile metal, meaning it are often stretched into long, thin strands without breaking. This makes zinc easy to contour to the form of the underlying substrate.
- High-temperature tolerance — Zinc is capable of tolerating temperatures of up to 120° F, which may help lower cooling costs.
- Control of hydrogen embrittlement — Zinc coatings are less vulnerable to the development of hydrogen embrittlement, a condition where the metal becomes brittle because of the diffusion of hydrogen within the surface. However, appropriate hydrogen embrittlement relief procedures should be implemented with the plating of high-strength metal fasteners.
- Friendly to the environment — Zinc plating is taken into account to be a comparatively eco-friendly process, especially in comparison to its cadmium counterpart. Zinc also offers the advantage of recyclability.
- Aesthetic appeal — Zinc plating can improve the appearance of an iron or steel part or component. The introduction of colours during post-treatment also can help you customize the design of the finished product.