Zinc plating is a fundamental process in precision engineering, used to protect metal from corrosion. It involves coating a metal part with a layer of zinc, creating a physical barrier that stops oxygen, water and other corrosive agents from reaching the underlying metal.
There are several types of zinc plating, including:
- Mechanical zinc plating: also known as sherardising, ideal for small components such as screws, nails and washers.
- Electrolytic zinc plating: a more common process in which the metal is coated in an electrolytic bath.
Zinc plating in precision engineering
Zinc plating is essential not only for corrosion protection, but also for improving the appearance of metal parts, giving them a bright, professional look. It is widely used in sectors such as automotive, electronics and marine engineering, where components must be highly durable.
Mechanical zinc plating takes place in a rotating drum, where zinc powder or granules are combined with a refining agent such as glass or ceramic. The process takes place at between 320 and 400 degrees. Thanks to the heat and rotation, the zinc particles adhere evenly to the metal, forming a protective layer of 5 to 30 microns.
The process is environmentally friendly, as it requires no electric current or aggressive chemicals, making it a sustainable choice for many industries.
The stages of mechanical zinc plating
Mechanical zinc plating has three main stages:
- Preparing the metal: the part is thoroughly cleaned to remove grease, oil and rust by sandblasting or acid washing.
- Coating: the component, together with the zinc and refining agents, is placed in a heated rotating drum, where the zinc melts and adheres to the metal.
- Finishing: the zinc-plated part can be phosphated or given other treatments to improve resistance and appearance.