HOW TO PAINT GALVANISED STEEL

Thinking of using paint to finish off exposed garage door beams or lintels to match your home's colour scheme? Unfortunately, paint does not adhere to galvanised steel. That's because the layer of zinc on the metal, which is designed to reduce corrosion, also rejects paint, causing it to peel away and shed.

 

This means that if it's not done properly, important steel components that are exposed at the bottom like lintels or garage door beams will need to be painted. Otherwise, it will lead to troublesome maintenance issues in the future. So, how do you paint galvanised steel properly to avoid these pesky issues down the track?

Well that's where Steel Builders comes in. With a common household product, and our steel building expertise, this step-by-step guide will tell you exactly what you need to know to produce some professional quality painting with your own two hands! Plus, we'll even tell you about how the professionals paint galvanised steel, including the types of paint to get the job done. 

Steel Builders | How to Paint Galvanised Steel

STEPS TO PAINTING GALVANISED STEEL - A DIY GUIDE

1. CLEAN YOUR STEEL

The first stage of our process is pretty self-explanatory and a familiar step in any painting job. Get yourself a rag and remove any oils, dirt, dust, salts, corrosion products, brittle material, soluble salts, and any other surface contaminants that could impact the texture. Remember, painting is always easier with a smooth surface because nobody enjoys brushing over bumps.

2. USING WHITE VINEGAR

With your galvanised steel looking clean as a whistle, it's time to introduce a common household product, white vinegar. Safer to use than your standard industrial solvent, white vinegar is non-toxic and works wonders for treating the surface of galvanised steel, promoting paint adhesion. Apply white vinegar to a clean rag, and wipe each surface down thoroughly to remove any residue.

3. WHAT TYPE OF PAINT TO USE ON GALVANISED METAL

You may have already selected your paint before embarking on this tutorial. However, it’s absolutely crucial to discuss your needs with your local paint supplier for advice on the best product. These products can be very different, and will change according to external factors like weather, humidity, geographical location and exposure to the elements.

Generally, if you plan on using acrylic latex paint, you’ll need to consider using primer, as this type of paint is not intended for use with galvanised steel.

For those looking to skip the primer phase, look for paint types that adhere better to steel. If you don't know what paint to use on galvanised steel, be sure to avoid using alkyd-based paints or oil-based primers. 

Can you spray paint galvanised steel? Spray paint works almost identically to regular paint, provided you’ve suitably primed the surface.

4. GET PAINTING

You heard us. Get painting! Having followed all these steps, you’ll be left with a smooth surface that is easy to paint.

PROFESSIONAL SURFACE PRE-TREATMENT FOR GALVANISED STEEL

The four recognised methods for professional surface pre-treatment for galvanised steel include T-Wash, Etch primers, sweep/whip blasting and weather. Each process involves different techniques to produce a sound substrate for a painting.

1. T-WASH

Considered the best pre-treatment method (despite the amount of time it takes to complete), T-Wash employs a modified zinc phosphate solution containing traces of copper salts. This solution reacts with the galvanised steel surface, leaving behind a dark grey or black discolouration. Once dry, a T-Washed surface can be left for 30 days before painting.

2. ETCH PRIMERS

Suitable for older, weathered galvanised steel, etch primers are another method for surface pre-treatment. 

3. SWEEP/WHIP BLASTING

This mechanical method blasts the galvanised steel at 40psi (2.7 bar) to prepare the surface using fine copper slag, J blast or carborundum powder. This achieves an ‘etch profile’ which, at a microscopic level, gives the paint something to adhere to on the surface. It’s a great way to ensure that there are minimal maintenance issues and peeling down the track.

The material used for sweep/whip blasting is finer than the one used for sand blasting and cleaning steel profiles of rust. This is to make sure that the galvanising is not damaged, and never exposes any raw steel underneath.

4. WEATHERING

The entire weathering process can take at least six months before becoming fully effective. Begin by removing surface contaminants with abrasive pads or brushes to prevent the zinc surface from being restored. 

Once scrubbed, the surface is given a hot detergent wash and rinsed with fresh, clean water. Once everything is dry, painting can begin. You should avoid weathering in marine environments with high chloride levels.

ORDER GALVANISED STEEL FROM STEEL BUILDERS

So there you have it! Painting galvanised steel is an incredibly easy task once you’re armed with the right knowledge. Start your next project today and shop online with us for speedy and reliable delivery across NSW, plus free pickup options for a range of galvanised steel products. Get a quote now! 

Got a project you’d like to share with us? We’d love to see how it turned out so tag us @steelbuildersptyltd on Instagram or Facebook.


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