Professionals whose livelihoods depend on the strength of their equipment know how important firm, durable metals are, and the consequences when the equipment breaks. For protection against corrosion, thermal spraying also called metalizing and dipped galvanizing (or hot-dipped galvanizing) are used.
Hot dip galvanizing produces a zinc coating on iron and steel products by immersion of the material in a bath of molten zinc metal. Hot dip galvanizing is a process involving 4 steps; surface preparation (removing mill scale and rust), pickling in acid, flux coating, and finally – dipping in molten zinc. Upon immersion in the zinc bath, the zinc and iron react metallurgically through a process called diffusion to create a progression of four layers consisting of zinc-iron alloys culminating in a surface layer of nearly pure zinc. This coating is actually harder than the base steel as hot dipped galvanizing becomes a part of the surface rather than a coating that sits on top. This bonding is called cathodic protection.
Since its introduction, hot-dip galvanized steel has been widely used in various industries such as construction and home appliances.
Hot-dip galvanizing provides a number of benefits to the steel it protects. The metallurgically-bonded zinc-iron alloy layers not only create a barrier between the steel and the environment, but also protect the steel. The cathodic protection offered by zinc means the galvanized coating sacrifices itself to protect the underlying base steel from corrosion.
However, despite its longevity and corrosion resistance, galvanized coatings are still subject to chipping, cracking, and similar damage.
In contrast, thermal spraying process involves the spraying of heated or melted metals onto the substrate surface. The metal is fed in either powder or wire form, heated to a molten or semi-molten state and sprayed as micro-sized particles. Thermal spraying enables the application of thick coatings and a high metal deposition rate.
The bond between a thermally sprayed coating and the substrate is primarily mechanical, and not metallurgical or fused.
Thermal spraying processes have been widely used for many years throughout all the major engineering industry sectors for component protection and reclamation. Recent equipment and process developments have improved the quality and expanded the potential application range for thermally sprayed coatings.
The main benefits and features of thermal spraying as a coating process are summarized below:
- Comprehensive choice of coating materials: metals, alloys, ceramics, carbides, polymers and plastics
- Thick coatings can be applied at high deposition rates
- Thermal spray coatings are mechanically bonded to the substrate – can often spray coating materials which are metallurgically incompatible with the substrate
- Can spray coating materials with a higher melting point than the substrate
- Most parts can be sprayed with little or no preheat or post heat treatment, and component distortion is minimal
- Parts can be rebuilt quickly and at low cost, and usually at a fraction of the price of a replacement
- By using a premium material for the thermal spray coating, the lifetime of new components can be extended
- Thermal spray coatings may be applied both manually and mechanized.
Clare Machine Work’s offers Corrosion Plus Coating™. A metalizing process that offers a superior coating to paint based applications with similar characteristics as hot dipped galvanizing. Future mobility of our service will offer the flexibility of on-site and dock-side coating options for existing structures, or when equipment is deemed too large for traditional galvanizing methods.