Linseed oil paint has a long tradition of use on different types of metals. For example, in the 17th century, it was common for artists to create their paintings on copper plate. Copper does not rust and therefore did not need to be rust protected. Iron, on the other hand, does rust, and various painting systems have been used throughout history to prevent or delay rust attacks on iron.
Like linseed oil, lead oil has recognized anti-corrosion properties, but lead oil has now almost completely disappeared from the market due to its toxicity. As a replacement for toxic pigments, we use a natural soil pigment called hematite, Fe2O3 (see also bloodstone, bloodstone ore, or iron luster). Our anti-corrosion paint is called Iron Minium. It contains boiled linseed oil and hematite, and we have long experience of its good protective effect against rust. Iron minium is brownish red, but it can easily be painted over with another color.
Painting on untreated iron/sheet metal, exteriors
- Protect bare iron by painting it with iron minium. Dilute the iron minium with 10% volume gum turpentine and apply a thin layer with a brush. Let dry for at least two days.
- Paint a second, anti-corrosion coat using undiluted iron minium. Let dry for at least two days.
- Choose one of our standard colors and paint with undiluted paint. Let dry for at least two days. (If you like the color of the iron minium, just continue to paint with it instead.)
- Apply the final coat using undiluted paint.
The linseed oil paint with the best properties for painting on metal is called Graphite. This pigment is a mineral carbon with a beautiful, dark anthracite gray color. In combination with rust-protective iron minium paint, graphite has proven to be outstanding in terms of long life and anti-corrosion properties.
Important things to know about sheet metal
There are many different qualities and types of sheet metal and metal used outdoors. It can be tricky to decide whether a metal surface can be painted with linseed oil paint. In 2006, the industry changed surface treatment of galvanized sheet metal, so the old rule of leaving galvanized sheet metal unpainted for a few years and then painting it no longer applied. There is still uncertainty about how to paint new galvanized sheet metal because experience is still lacking. If you want to paint roofing sheet metal with linseed oil paint, the advice is instead to choose pre-primed sheet metal from the factory, which is coated with a thin polyester primer. The sheet metal can be painted with linseed oil paint within about a year of installation. Other sheet metal types that work with linseed oil paint include galvanized sheet metal made before 2006, and aluminum, copper, and black sheet metal.