How to prepare a metal / steel fence before painting?

Steel & metal surfaces can be tricky for two reasons. Firstly they are usually pre-coated with some sort of anti-corrosion paint and that top coating is likely blistering away. You don’t want to overcoat that as when that fails, and it will, it will take down your new coating with it. Sanding that may not be sufficient but that would be the first thing you want to try. If the sanding (with a 80 grit sandpaper) is sufficient to remove the existing coating then great. Follow the following steps: Sand the surface to bare steel, and coat with FenceShield as soon as possible to stop flash rust.

Quick note about Flash rusts: they can happen fairly quickly. We can not tell you how quickly it happens as It depends on many environmental factors & conditions such as humidity and temperature but if I am going to venture a guess, you are most likely in Australia and if that is the case you probably have got around two hours after sanding a steel surface to apply the paint. The humidity is fairly high in most part of Australia and that moisture in the air speeds up the flash rust significantly.

There are a few ways to extend that time frame. Number one is applying a etch primer. Etch primers have been around for years and are a great temporary solution to stop flash rust. FenceShield adheres very well to most known etch primers. But that being said, you can get away without it if you plan your application well.

Below is my recommendation,

Step 1 – Pick a right day to do external painting. A sunny day with a low relative humidity is a good start.

Step 2 – Do your work section by section. Sand , prep, apply and move to next section. Remember FenceShield is UV stable and you wont get any colour changes if you apply part of the job today and the next tomorrow as long as you use the same colour / Batch.

Step 3 – Mix your paint in small batches so you can apply while it is liquid. Premature gelling interrupts the way a rapid set paint sits on the surface which results in drips, air pockets and other surface issues. Set your mixes based on your application speed and other environmental factor.

If the sanding is not going to work then the metal fence will have to be either mechanically abraded or blasted. Once the prep is complete , follow the same steps provided above.

One last tip – You get a much better result if spraying is an option for you. FenceShield is a thin material and sprays really nicely through airless, air-driven or pressure pot systems.

If you have any questions, send us a message here.

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