When Is Hot Zinc Spray Not Hot Zinc Spray?

Hot zinc spray is an excellent way of protecting steel. When HZS is applied by a skilled operator it will galvanise your item and form a protective layer against corrosion. However, some unscrupulous coaters can lead you to believe you are getting HZS, when in fact you are getting zinc powder primer or a wet zinc primer/wash.

This is why it is important to know when hot zinc spray is hot zinc spray. If you coat your metals in a ‘zinc primer’, then you can end up paying over the odds for something which isn’t going to protect in the way you hoped. Thankfully, we have produced this article to arm you with all the information you need to find a zinc substance which saves your metal products from damage caused by rust and corrosion.

Different Types of Zinc Coatings

There are many ways that zinc can be used to protect steel and iron. One of the most common and well-known methods is Hot Dip Galvanising. This is where a metal product is dipped into molten zinc. The zinc then hardens to give the metal product a protective coating.

Zinc can also be applied to steel or iron as hot zinc spray (HZS). Like hot dip galvanising, the result of HZS is that a metal product receives a coating of molten zinc from an arc gun which cools to form a protective layer.

A third option is zinc powder primer or wet zinc primer. The zinc powder is a cheaper and quicker application of zinc and is only intended as a mid-term protection and should not be used as an alternative to HZS or Galvanise protective layer. This is often what is used when coaters are trying to cut corners or hit an unrealistic budget with a quick turnaround.

Zinc powder primer does need to go through the oven to be cured before the topcoat can be applied.

Fourth option is Zinc phosphate Pre-treatment this is a multi-immersion system where the surface is chemically altered through a 6 stage process. This is not recommended for architectural steel products as it will not be robust enough for heavier balustrades or similar items.

Are you getting HZS?

Unless you’re an expert, it’s hard to tell. Unfortunately, there are a few unscrupulous people that know this, and they try and pass off zinc primer or zinc phosphate as HZS. Although it does give some level of protection, it is a very thin layer and if exposed to the elements will not stand up to the corrosion protection of HZS or HDG.

So, how can you tell? The easiest way is to look at the price. Hot zinc spray is typically more expensive than other processes, but that’s because it does a better job. If you’re being quoted for hot zinc spray and it is much lower than you’d expect to be charged, then take this as a red flag.
On average HZS can be £10-£20 per square meter more expensive than zinc primer, so please ask your supplier to state on the quote what process they will be doing. Also, check reviews on the company’s website and ask for testimonials from previous clients and get more than one quote, this will allow you to compare prices.

Don’t be afraid to shop around before you decide who to proceed with. The different price points will give you an idea of what to expect, and it’ll show you how to identify a company whose prices seem too low. Don’t be afraid to ask hard questions either. A good thing to look for in your estimate is the items being shot blasted to SA2 or SA3 standards, SA3 should be done for all HZS items. Also look for the application of an epoxy resin on top of the HZS before the topcoat is applied, this prevents degassing issues and allows for a better finish. Anyone familiar with the hot zinc spray process should be more than happy to answer any queries you have.

When Is Hot Zinc Spray Not Hot Zinc Spray?