How To Paint Rusted Metal?

We all have that one item in our home that leaves rust stains on our floor. I have two! Time to do something about it.

It's easy to look at a rusted metal item and think, wow! That piece of junk looks like it would be much easier to throw out than put in the effort to save. I can assure you that there is a great deal of self-satisfaction involved when you take that ugly, rusty piece and revive it. A rusted metal item can be preserved and revitalized with proper cleaning, priming, and painting. 

Painting Rusted Metal 101

Can you paint directly onto the rust itself?

It’s always better to sand the rust off till you only have bare, exposed, un-rusted metal to paint on. It is however possible to paint directly on top of the rust if the metal items still have enough underlying structure, and the surface is stable.

Will the rust show through the paint?

Untreated reddish-brown rust can bleed through paint, especially lighter colour paints. The rust conversion primer turns the rust black, and its polymers seal the rust against bleeding. If the metal is properly primed, the rust should not show through the paint.

Can you stabilize the rust before painting?

Oxygen, water, and iron are required for oxidation, this is the process that creates rust. 

Using a rust conversion primer before painting halts oxidation. Tannins in the rust converter turn the rust black and stop the oxidation. Polymers in the converter seal the metal against oxygen and water. Make sure that all sides of the metal are coated, as even a small uncoated section is enough to allow oxidation to continue.

Please Take Note: Safety Considerations

Painted items with rust may have been earlier painted with lead-based paint. Homes built before 1978 may have lead-based paint. Metal items popular with crafting and restoration such as patio chairs, tables, signs, and housewares may be painted in lead-based paint, too. Observe all safety techniques for working with lead-based paint.

How to Paint Metal: What You'll Need

Equipment and Tools:

• Wire Brush

• Sandpaper (Corse for Cleaning and Smooth for Sanding)

• Putty Knife

• Latex Gloves

• Eye and Breathing Protection

• Hammer

Materials:

• Degreaser

• Rust Converter Primer

• Water- or Oil-based Paint

Instructions

Remove Loose Rust

Use the wire brush, begin lightly, removing only the rust layers that come off easily. Use a putty knife or a five-in-one tool to scrape away large sections of rust. If the area is large or particularly difficult, use a wire wheel attached to a hand grinder instead of brushing with the hand brush.

Once the large, rusted sections are gone, tap the metal lightly with the hammer to assess whether the metal is strong enough to be painted. At this point structurally unstable metal will collapse.

Sand the Rust

Sand the rusted metal to remove more of the rust and to smooth down the surface. Frequently clean off the surface and the sandpaper. Sand a few inches beyond the rusted area, as well. Small, corroded areas can be filled in and smoothed over with a fiberglass-based filler.

Clean the Surface

Use a degreaser to clean off any grease or oil. It is difficult to get a rusted area perfectly clean, so the goal is to remove most of the flakes and dust.

We recommend the following product for the job:

Duram NS2 Galvanized Iron Cleaner is a ready-to-use cleaner and surface etching compound for maximum adhesion, that removes grease, dirt, surface oxidation (white rust) and impurities from weathered galvanized iron. NS2 Galvanized Iron Cleaner treats new galvanized iron, mild steel, aluminum, chromadek and removes the oily surface coating. Clean up is a breeze, with a quick water rinse.

Use: 100 - 150 Grit sandpaper to prepare the surface

Standard Colours: Clear

Available Sizes: 1L and 5L

Apply the Rust Converter

With the rusted area cleaned off and dry, spray the rust converter over the rusted area and a few inches beyond. Apply a thin coat and avoid drips. Many rust converters are clear when they are first applied, then turn black. Let the rust converter dry for at least 24 hours.

We recommend the following product for the job:

Duram NS1 Rust Buster is a rust converter and primer that instantly converts rust to a primed, paintable surface. Use on corroded iron and steel, particularly in difficult, hard to reach areas.

NS1 Rust Buster reacts with rust by neutralising the iron oxide that causes rust and converting it into a stable, solid compound that’s ready for further priming and painting.

Duram NS1 saves time and labour, works in seconds, neutralises red rust to a blue-black hard film it has excellent adhesion, preserves, protects, and conditions metal, resistant to flash rust with quick and easy water clean-up.

Ideal for roofs, gates, fences, handrails, burglar bars and structural steel. (Interior and exterior use.)

Use: 220 Grit Water Paper to prepare surface

Colour: Cream coloured liquid, which turns blue-black when reaction is complete.

Available Sizes: 500ml, 1L & 5L

Paint the Metal

You are now ready to apply the Top Coat. Some rust converters may require only an oil-based top coat, not a water-based paint; consult the rust converter instructions.

We recommend the following product for the job:

Duram DTM is a convenient, direct to metal adhesion primer, anti-rust coating and attractive topcoat in one that offers maximum rust protection.

Product uses:

Convenient 3 in 1: Adhesion primer, anti-rust coating and attractive topcoat in one. 

For new, corroded and previously painted metal. Apply direct to bare mild steel, stainless steel, wrought iron, galvanized iron, aluminium, zinc, copper and brass. 

Residential and light commercial metal surfaces, gates, fences, railings, balustrades and handrails, doors, windows, burglar bars, trims, shutters, garage doors, outdoor furniture, playground equipment, lighting fixtures, piping, farm implements, machinery and storage tanks. 

Interior and exterior use:

Advantages:

Maximum rust protection in a convenient one can application - saves time and effort. Excellent adhesion provides a tough long-lasting barrier, with an attractive enamel finish in a variety of finishes and colours.

Rapid drying with UV - and weather-resistant properties, this abrasion and scratch resistant product offers your metal up to 8 years protection, while being flexible to withstand varying temperatures.

Colour: Available in over 10 colours.

Finish: Smooth finish, Hammered finish

Available Sizes: 250ml, 500ml, 1L and 5L

All the products and materials that have been used in this article are available instore from Build it Gansbaai/Hermanus or on the online store www.buildit-store.com with free local delivery in the Overstrand area, for building materials, do-it-yourself home improvement tools, and expert advice.

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Build it Gansbaai/Hermanus offers added value services in respect of hardware retailing; embracing all activity within the building materials industry, focusing specifically on the building of; urban, township, rural housing as well as all home improvements and do it yourself.

Build it is a division of the SPAR Group Limited South Africa. A voluntary trading group of individually owned retail stores with more than 10 000 employees across the group, we currently have stores in South Africa, Namibia, Swaziland, Lesotho and Mozambique with plans to expand into Botswana and Zambia in the near future. We view ourselves not only as a supplier of materials, but as a partner to our valued customers in accomplishing their building or renovating projects.