As its name suggests, zinc plating, or galvanizing, is a process in which a zinc coating is applied to a metal surface (usually steel but others as well). How, but above all why, is it done? What is it used for?
What is the purpose of galvanizing?
Galvanizing is used to protect metals from galvanic corrosion by hindering the formation of electrolytes with anodic action at the edges.
In fact, since zinc is less electronegative (i.e. less noble) than steel, it acts as a sacrificial anode in the event of electrolytic corrosion. Zinc plating guarantees an excellent quality coating and represents a valid alternative to more expensive galvanization treatments such as chrome or nickel plating.
Hot, cold, electrolytic or spray zinc plating: what is the difference between these techniques?
In practice, zinc plating can be applied using different techniques, but here we describe the most common.
Hot-dip zinc galvanizing
The zinc layer is applied hot, that is, through immersion in a bath of molten zinc at a temperature of about 450°C (not to be confused with continuous hot dip galvanizing, which involves steel strips or wire).
Electrogalvanizing (also known as zinc electroplating)
This process occurs through immersion in an electrolyte solution containing zinc salts. It is preferred for carefully hardened steel parts and precision parts.
Spray galvanizing
Spray galvanizing is carried out by applying atomized molten zinc using guns equipped with a melting and spraying device and a device to feed in the zinc wire.
Cold galvanizing
When it comes to cold galvanizing, it is perhaps improper to talk about galvanizing in the strict sense, since from the technical point of view, this more properly involves a resin-based synthetic paint rich in zinc. The results are obviously not comparable to those of hot dip galvanizing, but this is a valid alternative in difficult-to-treat environments.
Spin galvanizing and rack galvanizing
Based on the metal, spin galvanizing is suitable for small parts and rack galvanizing for larger or particularly delicate products.
How long does the protective effect of galvanizing last?
Hot dip galvanizing is a useful process for protecting steel from its enemy number one: rust. Corrosion gradually destroys metals, especially when exposed to unique environments. The environment surrounding the product certainly also impacts the duration of the galvanization.
Pre-treatment of the metal is important and paint is often applied after galvanizing for further protection. But are there any methods to make the effect last longer or make galvanizing more effective?
Although hot dip galvanizing was discovered more than a century ago, it is still an effective technique that provides good results against metal corrosion.
As in all industrial sectors, and even others, subsequent inventions have led to new techniques. This field of research is currently investing heavily in fluoropolymers, which have shown incomparable versatility in protecting metals from rust.
In particular, industrial Teflon coatings can be applied to all metals and also non-metallic materials such as glass, fibreglass, rubber, plastic, etc. Teflon also has a low friction coefficient (ranging from 0.05 to 0.20 depending on the load conditions, sliding speeds, etc.). On a practical level, Teflon coatings are also easy to clean because they are oleophobic.
Finally, industrial Teflon coatings are heat-resistant and non-stick. They can have high electrical resistance (and, indeed, be used as antistatic coatings using specific techniques), or be conductive, depending on the particular needs.
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