How to Paint Galvanised Metal
It’s easier than you may think to keep your galvanised surface looking good. Typically the issue with painting it that a galvanised surface is very smooth, which then makes it difficult to get paint to stick to it. On new galv there are also sometimes contaminants such as oil and grease let over from the manufacturing process. But with the right preparation, and a few clever products, it can be really easy to get a great finish.
Why you might need to paint it.
Unpainted galvanised metal can last for decades on its own, but there are other reasons why you may want to paint it. Often this type of steel is affected by something called white rust or salts: this is where a white, powdery deposit forms where the galvanised surface has been exposed to rain, condensation or dew. If left alone then this rust will eat into the metal and cause big problems further down the line, which is why it is often a good idea to apply a coating that will protect the surface.
However the most common reason why people want to paint galvanised metal is to enhance the appearance of it. Sometimes people are looking to maintain the galvanised appearance, but they want to brighten it up, or they may be looking to change the colour. Whatever the motivation behind doing it, a coating on top of Galv will enhance the appearance and offer additional protection.
Don’t skip the prep!
The most important thing is always going to be the preparation (as is the case with most paint jobs). With difficult to paint surfaces it becomes even more important. When a surface hasn’t been prepared properly it can lead to the paint blistering or peeling which is obviously not what we want. The job then gets harder and more expensive, so it’s much better to get it right the first time.
The preparation is slightly different depending on whether or not the surface is new or weathered. So we’ve included both for you. Just follow what seems the most appropriate for your situation.
New Galv: New galvanised metal is harder to paint than weathered galvanised metal. If the surface is less than a year old then it will not have have very much exposure to the elements, which means it will still be very smooth and contain contaminates from he manufacturing process, which then makes it difficult to paint. but with a bit of extra prep it can be done.
What we usually recommend to do is to clean the surface using an Alkaline cleaner (ND14) and then overcoating the cleaned surface with an adhesion primer (3202). Once the primer has been applied then the paint will be able to stick to the primed surface. The topcoat that you will need depends on the environment that the surface is in, but if you aren’t sure what you want then our technical team are always willing to help.
The other way to do it is to use an acid etch to create a roughened profile on the surface. We have products that will do this (T Wash), but we don’t tend to recommend it because by allowing the acid to eat into the surface you are damaging the zinc surface that you’re trying to protect.
Weathered Galv (Over 12 months old): Weathered galvanised surfaces are usually a lot less smooth when compared to new galvanised metal. This makes it far easier to paint, although there is still a certain level of prep work that’s needed to make sure the paint system will last.
There won’t be any contaminates on the surface from the manufacturing process left over, but there will be dirt/grime from exposure to the elements. But once the surface is cleaned then it can be painted with either a one coat specialist paint, or an adhesion primer followed by the topcoat of your choice.
Previously painted Galv: As with all previously painted surfaces you need to make sure that any flaky paint has been removed from the surface, and that the surface has been sufficiently cleaned. But then once the surface is viable then it is ready to be painted. Any spots of bare galv may need an adhesion primer applying to them, but then they are ready to have a topcoat of your choosing over the top.
And now the fun part.
When the prep work is all done then you’re in a position where you can focus on the finish that you want.
Galvanised appearance: There are a lot of sprays and paints that will give your surface a refreshed galvanised appearance. Both a standard galvanised finish, and also brighter zinc aluminium finishes.
Coloured appearance: We have a one coat vinyl system that can be applied straight onto galv. Otherwise, once an adhesion primer has gone onto the galvanised surface then you can apply almost anything over the top. Just make sure that the topcoat you choose suits the environment that it’s going on to.
If you need further advice on how to paint galvanised metal then give us a call and one of our technical team will help.