An interesting part of designing these Corten steel planters is that they're completely safe for growing food. The amount of iron oxide released into the soil during the rusting process is non-toxic and will not adversely affect plants.
What is Corten Steel?
As mentioned previously, Corten steel is a weather resistant steel that can also be called ‘Atmospheric Corrosion Resistant Steel’, and it is its alloying elements of copper and chromium that provide this level of atmospheric resistance.
Corten steel has a distinctive orange color, which is caused by the chemical composition forming a protective rust layer when exposed to extreme environments. There are two main grades of Corten steel; Corten A and Corten B.
Let’s also discuss the differences between corten A steel and corten B steel. They’re mostly the same material, but Corten A or the original COR-TEN received the addition of phosphorus, making it more useful for building facades and gas flues. Corten B is weathered steel that does not have this addition and is better for large structures. There are other slight variations between the chemical compositions of the two types of weathering steel.