How to Paint Rusted Metal

How to Paint & Prepare Rusted Metal to Last

Some rust and corrosion are more pronounced, ranging from contact areas to structural supports, including metal handrails, steel exterior doors, exterior metal hardware, and steel brick lintels.

When we see rust, it’s unsightly, and instinctively, we want it removed. But the truth is that the damage will already be underway by the time the rust is visible. While processes and preparations help remove rust, rusted metal ultimately requires protection from future exposure to prevent further rust. We will explain how to paint rusted metal surfaces and prepare them for painting.

What Causes Rust?

Steel is a commonly used metal. It is used for building materials, exterior home furniture, and more. While steel is solid, it has limitations. The main drawback is rust. 

Steel’s composition includes iron and carbon. A combination of air and water causes the iron particles in steel to rise and flake off at an accelerated rate. 

Most exterior steel used on homes, such as doors, has a rust-inhibiting primer. Red Oxide primers have been used for years, but only slow the rusting process. No primers will exceed, keeping exterior metal substrates dry. However, oil-based industrial paints provide longer protection and reduce future maintenance. 

An industrial paint will last longer and replicate a factory-like finish. Powder-coating metal also offers enhanced metal protection. 

Industrial Coatings & Non-Industrial Coatings

Applying a durable, metal-specific exterior paint will make painting metal easier and improve the results. While a few store-bought metal paints provide moderate performance for homeowners, they are not considered high-performing coatings.

Manufacturers such as Rustoleum have a brand-recognizable reputation, providing fast and straightforward solutions for homeowners. While Rustoleum does offer industrial products, Rustoleum paints found in home improvement stores are not recognized as industrial finishes. 

Industrial coatings must meet specific OEM standards, whereas non-industrial paints are not required and have only minor criteria beyond hazardous material labeling standards. 

The Best Coatings For Rusted Metal

When deciding which coating to use on metal, we aim for a balance between usability and durability. When the balance between the two shifts heavily toward being difficult to use due to viscosity, drying time, or specialized tools required, we recommend hiring a professional painter. 

Metal coatings include acrylic, alkyds, epoxies, and urethanes. Industrial urethanes provide ultimate durability without compromising usability, unlike epoxy. 

If you are a professional house painter or an experienced homeowner, here is a list of a few industrial coatings, primers, and solution treatments worth considering. The following coatings provide durability and well-balanced application measures.  

Rust Inhibiting General Use Metal Surface Primers & Solutions

• SW Kem Kromik Primer
• PPG Primers
• Skyco Rust Treatment

Industrial Metal Surface Top-Coats

• SW Pro-Industrial Urethane Enamel
• BM Corotech Urethane Enamel
• Rustoleum DTM Epoxy

Tips For Painting Rusty Metal

Painting over rust will not last. For best results, you must remove the rust. However, an entire removal can be time-consuming and expensive. In most cases, combining sanding and scraping is common. 

You can also use a rust-inhibiting solution with light scraping to significantly improve surface conditions. While a clean surface is essential for preventing further rust, it must be dry, regardless of how extreme or gentle the rust-removal process you choose is. If possible, choose a day with low relative humidity.  

Note: The purpose of this article isn’t to provide comprehensive safety details. However, always protect yourself by wearing a mask and gloves. Rusted iron particles are something that you do not want to inhale.

The Best Process to Paint Rusted Metal

1. Blast exterior metal surfaces using a pressure washer to remove mold and mildew. Use a non-bleach mold-killing solution, as bleach contains sodium. 
2. Remove loose rust particles with a wire wheel for machine use or a wire brush for manual use. 
3. Sandblasting can also be utilized for commercial or large applications.
4. You can apply a rust-inhibiting solution to further prepare the surface. 
5. Wipe down the surface to remove all debris and discoloration.
6. Sand the entire metal structure using 120-grit sandpaper.
7. Prime the entire metal surface. (Make sure to use the appropriate primer to adhere to the existing substrate.)
8. Top-coat with an industrial-grade coating. (For ultimate results, apply the first coat with a brush and spray the second coat when two coats are necessary.)

Note: When painting dark colors, cover the surface after the coating is dry. This will mitigate potential water spots caused by evening storms or high early-morning dew points.

Tools that Will Expedite the Process

• Angle Grinder
• Dremel Tool/ Sander
• Spray Bottle
• Titan 440 Paint Sprayer
• Purdy Pro-Extra Paint Brush

Comparing Coatings For Metal

Epoxy vs. Powder Coating

Whether painting an industrial coating or applying a solution, rust-inhibiting properties are essential to painting metal exposed to rust. However, not every metal surface will benefit from powder coating or a 2-part epoxy. While they may be the most effective applications, they are not cost-effective or always viable. 

Powder coating is typically performed in a shop, so the metal structure would need to be removed. Two-part epoxy’s higher viscosity and very fast dry times make it more challenging to apply. In short, epoxies are fantastic, but brushing a dark-colored epoxy on a hot day is not happening.

Urethane Enamel

Urethane enamel provides the most durable coating and can be easily applied to multiple surfaces using various methods.

Conclusion

When considering durability, cost, rust elimination, and color retention, multiple products are available. We offered options and procedures to bridge the gap, making the process accessible and durable with an industrial-grade coating. 

Local store sales clerks’ or painters’ opinions can be pervasive. We hope this article has helped and applies to your situation. If you need service in the Raleigh area, feel free to contact us anytime!