Powder Paint Coating “What lurks beneath”

When choosing the base material and pre-treatment options before ever applying the powder this is what will decide the longevity of the paint coating. You can place 2 metal parts side by side that will look exactly the same in appearance but what lurks beneath is what will decide how they will perform in the field environment. If one part has had the correct material choice and the right pre-treatment and the other a poor material choice with just basic cleaning applied the performance difference will be significant.

For many industries, lengthening the lifespan of essential machinery is a critical concern. Logically, powder coating is a time and cost-effective way of doing so. Of course, this process has to be done right to be worthwhile, which is why a zinc phosphate pre-treatment process is considered a key element of any preservation policy.

At first glance, it might seem that the regular cleaning is sufficient before powder coating because it removes the oil and dirt build-up, as well as welding scale and a host of other soils. But even with the surface cleaned thoroughly, adhesion can still be improved.

Powder coating is one of the surest ways of preserving a mechanical part, offering greater protection than a wet paint option. That is because the polymer that is sprayed onto the surface is more durable and more adhesive than wet paint is. The powder used for the coating could be a type of thermoplastic or a thermoset polymer, but when cured under heat it develops a skin that creates a hard finish.

But how does zinc phosphating make a difference? Why is it such an important part of the process? There are several points that underline why.

What Is Zinc Phosphating?

In essence, the process subjects a metal to an acid that attacks the surface before a material containing the metal substrate and phosphates settles back down onto it. The result is an inert surface that is microscopically rough.

As a result, the surface offers more effective bonding, which can be maintained even after being scratched. This means there is a very small chance of flaking or peeling, so the risk of moisture and air making their way under the coating – and therefore rusting – is reduced dramatically.

Zinc Phosphating is carried out after the surface has been cleaned thoroughly with the use of a proven alkaline-based chemical cleaner. The cleaner contains surfactants to lower surface tension, with the spray pressure and water temperature both key considerations.

The second stage is a rinsing stage, when the soils are removed. Then attention can be turned to the phosphate pre-treatment.

Benefits of a Zinc Phosphate Pre-Treatment

So, why make such an effort to Zinc Phosphate a metal surface? Well, there are a series of scientifically proven benefits that make the investment in time alone worthwhile. The key benefits are:

  • Improved Powder Coating Adhesion – the treated surface is made rough, and therefore makes sticking not just easier but more effective.
  • Improved Coating Base – because of greater adhesion, the metal part is more effectively protected and a longer useable life.
  • Improved Corrosion Inhibition – with the powder coating sticking more effectively, air and moisture are both more effectively locked out. Thus, the risk of rusting and corrosive damage is drastically reduced.
  • Improved Finish – with the coating sticking so effectively it envelops the metal surface, the quality of finish is also improved. And with a smooth, uniform finish, cleaning becomes easier too.
  • Neutralizes Surface pH – leaving a metal surface untreated leaves it susceptible to a host of faults that allow negative and positive charges to coexist.

How we can help

So it is clear that the choice of the correct steel substrate and pre-treatment option are essential to getting the best performance from your powder coat. Here at Keltech we can help advise clients at the design stage how to incorporate both. This involvement can help reduce costs whilst getting the best results.

We preform daily testing to ensure our processes are under control at all times. Weekly samples are sent for independent salt spray testing and data packs are used at regular intervals to ensure  optimum performance. We use globally recognised brands: Chemetall Chemicals, Valspar, Akzo Nobel and HMG powders but to name a few.

At Keltech we have 20 years of Powder Painting experience. We paint components for major OEM’s whom supply product throughout the world to some of the harshest of environments.

Looking for a superb, long lasting paint finish? Dont hesitate to contact  our Business Development Manager Seamus Lawlor who will more than delighted to help. Seamus.lawlor@keltech.ie



See All Insight