Galvanising is often the default choice when it comes to corrosion protection, but is it really the best option for every job? After some conversations with industry contacts and digging into our own experience, it turns out that hot dip galvanising (galv) might actually be costing you more time, money, and quality than you think—especially when you’re aiming for a smooth, powder-coated finish.

Let’s break it down.

The Cost of Galvanising vs. Hot Zinc Spray (HZS)

If you’re weighing the financial side of things, it might seem like galvanising is the cheaper option at first glance. On average, galvanising costs around £40 per m², while Hot Zinc Spray (HZS) comes in at around £60 per m². That’s a £20 difference, but here’s the kicker: galvanising often leads to extra costs further down the line. Why? Because of the need for fettling.

In our experience, if you’re planning to powder coat a galvanised item, you’ll need to fettle it first. This means sanding, grinding, or smoothing down that thick, rough zinc layer so that the topcoat can be applied smoothly. And guess what? This process not only adds time and labour but also removes a significant portion of the zinc you’ve just paid to apply.

Fettling: The Hidden Cost of Galvanising

Let’s talk about fettling. Fettling, in the context of metalwork, means mechanically smoothing the surface of a galvanised item to prepare it for coating. In theory, this is fine—except that in the fettling process, you can lose up to a third of the protective zinc coating. We’ve done Elcometer readings here at NSP, and we’ve seen that approximately 30-35% of the galvanising is removed during fettling. That’s a huge chunk of the protective layer you just paid for!

In some cases, the initial galvanised coating is already quite thin. We’ve seen jobs come in with just 70-90 microns (µ) of zinc, and some with only 40µ. By the time fettling is done, you’re left with a compromised protective layer, and this essentially voids the galvanising warranty because you’ve “mechanically touched” it.

So, what happens next? You’re left with a thinner protective layer, more vulnerable to corrosion, and you’ve still got to pay to powder coat it. In some cases, your galvanised item might not even have enough zinc left to provide meaningful protection once it’s been fettled smooth.

NSP HZS dark flare

Why Hot Zinc Spray (HZS) is the Smarter Choice

Enter Hot Zinc Spray (HZS), also known as Arc spray. While HZS costs more upfront at £60 per m², you avoid the need for fettling entirely. This means the zinc layer remains fully intact and offers full protection, providing a smooth base for the powder coating procedure. It’s all-in-one protection without the hassle of fettling, and you retain the zinc layer’s full integrity, ensuring your item is truly protected from corrosion.

Here’s why HZS is a better option in the long run:

  1. No Fettling Required: With Hot Zinc Spray, you skip the fettling process entirely. The surface is already smooth and ready for the topcoat, saving you time, money, and effort.
  2. No Zinc Loss: Because you’re not grinding or sanding away the zinc, the protective layer remains fully intact. You don’t lose any of that all-important zinc coating that protects against rust and corrosion.
  3. Perfect for Powder Coating: The even, unblemished surface created by Hot Zinc Spray means you can apply a powder coat without worrying about lumps, bumps, or rough patches.
  4. Cheaper Overall: When you factor in the cost of galvanising (£40 per m²), plus the fettling and the risk of voiding the warranty, the Hot Zinc Spray process at £60 per m² quickly becomes the cheaper, more effective option. You get a smooth finish, a fully intact zinc layer, and less hassle overall.

In fact, at NSP, we offer fettle and coat services at £45 per m², or £85 all-in for a job that’s been galvanised, fettled, and coated. That’s £85 per m² for a process that will likely reduce the protective zinc layer and take more time, compared to £60 per m² for a clean, smooth HZS finish right from the start. The maths speaks for itself.

NSP HZS man with red helmet on and spray gun

The Drawbacks of Galvanising

To recap, here are the key reasons why hot dip galvanising may not be the best choice, particularly when you’re after a decorative, powder-coated finish:

  1. Uneven, Rough Finish: Galvanising leaves an uneven, thick zinc layer that’s hard to coat without extensive fettling.
  2. Zinc Loss from Fettling: By the time fettling is done, you may have lost a third of the protective zinc layer—making the item more susceptible to corrosion.
  3. Void Warranty: Fettling mechanically alters the zinc layer, potentially voiding any protective warranties that came with the galvanising.
  4. Higher Overall Costs: When you add in fettling and coating costs, galvanising becomes more expensive and time-consuming compared to HZS.

Hot Zinc Spray (HZS) for the Win

When you need a smooth, aesthetic finish that’s fully protected, Hot Zinc Spray (HZS) is clearly the superior option over traditional galvanising. At £60 per m², HZS offers better value for money in the long run, saving you from the additional time and expense of fettling and ensuring the protective zinc layer remains intact. No need for grinding down the surface, no loss of protection, and no risk of voiding warranties.

NSP HZS close up of being sprayed on metal

Here at NSP Coatings, we exclusively offer Hot Zinc Spray at our factory because we believe in maintaining full control over the quality of our work. We don’t offer this service on-site, ensuring that each job is completed to our high standards. With our dedicated Quality Assurance (QA) department and in-house transport fleet, we can confidently deliver your project coated to perfection—on time and in pristine condition.

And here’s the real clincher: At NSP, we offer an exclusive 60-year Anti-Corrosion guarantee when items are coated to our specific specification, including the use of Hot Zinc Spray (HZS). So, not only are you getting superior protection, but you’re also covered for decades to come.

For more details about our 60-year guarantee and how HZS can save you time, money, and headaches, get in touch with us today. We’re here to help you get the best possible finish for your projects!