Hot Dip Galvanising vs Hot Zinc Spray

What’s better? Traditional Hot Dip Galvanising? Or Hot Zinc Spray?

The process of galvanising has been around for over 150 years and was named after the Italian scientist Luigi Galvani.

Both dipping and spraying apply corrosion protection to steel, but what is best for your item?

Firstly, let’s look at how the zinc is applied to the base metal.

Hot Dip Galvanising process

Galvanising is the process of submerging the item in molten zinc or as it’s commonly referred to ‘dipping’. A bath of molten zinc is used to dip the items and the coating builds up very quickly.

Hot Zinc Spray Process

Hot zinc spray uses a gun as the applicator. This is achieved by colliding two zinc wires that have positive and negative charges, thus causing an arc reaction and the zinc is turned molten. Using compressed air blasting or spraying it onto the surface at low heat.

Knowing what process is best for your items will need to be determined by several factors, we have listed some of the facts for each process below, but if you are not sure we would always advise you to ask an expert’s advice.

Facts about Hot Dip galvanising

• It can only be carried out off-site
• You might be restricted by the size of the bath v’s the item
• Items can be too small to dip
• Because the zinc is molten, the bath is very hot, and it can cause distortion of the base metal
• Again, heat can cause welds to expand
• In some instances, can be a lower cost 
• Its protection typically last 20-25 year but can last more than 50 years
• Because the item is submerged it can fill hollow tubes and hard to reach areas
• galvanizing has an abrasion resistance ten times better than organic paint coatings
• Using the dipping process can be quick depending on the coverage thickness required
• Holes need to be drilled in the items to allow molten zinc to escape hollow sections
• The tanks need to be kept molten using more fuel/energy when not in use
• If items are to be painted after galvanising, they will need to be fettled, this will reduce the anti-corrosion protection.

Facts about Hot Zinc Spray

• It can be used in a factory or out on site
• No limited to the size, large or small of the item to be coated
• Low heat input means, less risk of thermal distortion
• Lower risk of thermal metallurgical degradation
• The process is not limited to zinc
• The thickness can be varied across the item if needs be
• Sealed tubes can be coated without the risk of explosion
• No effluent disposal problems
• It can be used to spot and treat metal
• Fuel / Energy is only used during the application process
• If items are being painted, they will need no fettling just a light rub over to clean.
• No drips or lumps

At NSP Coatings we use the Hot Zinc Spray method of galvanising and for the work, we carry out we think it gives a better finish and when coated to a specific thickness, we offer it as part of our 60-year guarantee.

If you are unsure if your item should be dipped or sprayed, please speak to us as we are happy to offer an impartial opinion.

If the dipping process is right for your item, we can recommend local suppliers that we trust to do a good job.