How to Paint Rust: Preparing & Restoring

Painting Rusted Metal: The Process Made Easy

Whether the rust persists on the inside or out, every home has a potential for rusted metal surfaces. Some rust and corrosion are more pronounced, ranging from contact areas to structural supports such as metal handrails, steel exterior doors, exterior metal hardware, and steel brick lintels. Here we will explain how to paint rust by thoroughly preparing the surface.

When we see rust, it’s unsightly, and instinctively we want the rust removed. But the truth is once the rust is visible, the damages are already well underway. 

While processes and preparations will help with the rust removal process, ultimately, rusted metal requires protection from future exposure resulting in rust.

Here we will explain how to paint rusted metal in a practical, manageable way that will last a long time!

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. 

The composition of steel includes iron and carbon. A combination of air and water causes the iron particles in steel to rise and flack off at an accelerated rate. 

Most exterior steel materials used on homes, such as doors, have a layer of primer that resists rust. Red Oxide primers have been used for years but merely slow the process of rusting. 

No preliminary precautions will exceed, keeping exterior metal substrates dry. Although, professional protective coatings protect longer, better, and reduce future maintenance. 

A professional industrial coating will not only last longer but, in some cases, will emulate the appearance of a factory finish. If you have no intentions of tacking the process yourself, and the metal is transportable, powder coating offers a durable factory-like finish as well. 

Industrial Coatings & Non-Industrial Coatings

Applying a durable exterior metal-specific paint will make the task at hand more manageable, and you will ultimately be happier with the results. While a few store-bought metal paints provide moderate performance for homeowners, they are not considered high-performing coatings.

Manufacturers such as Rostelum have a reputation and are brand recognizable to almost any American do-it-yourselfer. They provide 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, while non-industrial paints are not required and have minor criteria other than hazardous material labeling standards. 

The Best Coatings For Rusted Metal

We will say there is a balance between usability and durability when ultimately deciding which coating to use for metal. When the balance between the two starts to lean heavily toward being hard to use due to viscosity, dry time, or special tools required, we recommend hiring a professional painter. 

Coating as such are typically not for the faint of hearts.

Metal coatings rang from acrylic, alkyds, epoxies, and urethanes. Industrial urethanes provide ultimate durability without compromising usability as epoxy would. 

If you are a professional house painter or 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 completely remove the rust. However, an entire removal can be time-consuming and expensive. So, in most instances, a combination of sanding and scraping is most common. 

You can also use a rust-inhibiting solution in conjunction with light scrapping that will significantly improve surface conditions. 

While a clean surface is essential to resisting further rusting, the surface must be dry no matter how extreme or light the rust removal process you choose. Choose a day when the relative humidity is low, if possible.  

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 wire brush for manual use. 
3. Sandblasting can also be utilized for commercial or large applications.
4. You can opt to apply a rust-inhibiting solution to prepare the surface further. 
5. Wipe down the surface removing 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 with dark colors, cover the surface after the coating is no longer wet. Covering will mitigate potential water spots caused by evening storms or high early morning due points.

Tools that Will Expedite the Process

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

Comparing Coatings For Metal

Whether it is painting an industrial coating or applying a solution, rust-inhibiting properties are essential to painting metal that has been exposed to rust. But not every project deems powder coating or a 2 part epoxy coating. While they may be the most effective applications, they are not cost-effective and are not always viable. 

Powder coating is typically done within a shop. Therefore, the metal structure would have to be removed. That is certainly not happening with a brick lintel and would be costly just for a metal door.

Two-part epoxies are notorious for thicker viscosities and have super-fast dry times. Meaning, epoxies are much harder to apply. In short, epoxies are fantastic, but brushing a dark-colored epoxy on a hot day just is not happening.

A urethane enamel provides the most durable coating that can be easily managed and applied to several surfaces by multiple means of application.

When considering durability, cost, rust prominence, and color, there are multiple products. We offered the options and procedures to bridge the gap, making the process accessible and lasting with an industrial-style coating. 

The opinions of local store sales clerks or painters can be pervasive. We hope this article has helped guide and inform you in a way that is applicable to your situation. 

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