It’s all too easy to look at a rusted metal item and think that it cannot be saved. Bumpy, flaking rust hardly looks conducive to a beautiful paint job. But a rusted metal item can be preserved and revitalized with proper cleaning, priming, and painting. With the right techniques, you’ll be able to preserve most rusted metal items that still have enough underlying structure.
Basics of Painting Rusted Metal
Can You Paint on the Rust Itself?
Whenever possible, it is always best to sand off the rust and expose only bare, unrusted metal for painting. But it is possible to paint directly on top of the rust, as long as the surface is stable. This paint should always be laid on top of a primer designed for metal.
Will the Rust Show Through the Paint?
Untreated reddish-brown rust can bleed through paint, especially lighter color paints. Rust conversion primer turns the rust black and its polymers seal the rust against bleeding. As long as 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—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 areas of the metal—even the back side—are coated. Even a small uncoated section is enough to allow oxidation to continue.
When Is an Item Too Rusted to be Painted?
Generally, items that are deeply pitted or pinholed are too rusted for painting. Often, an item might look promising at first. Yet scraping and brushing take off layer after layer of rust, revealing no substantial metal underneath.
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.
Source: The Spruce