Rust-proof cast iron outdoors.

[Albireo]

Hello!
I'm planning to put cast iron covers on the drainage pipes that stick up on the lawn (3 pieces).
Even when I bought them, they looked a bit rusty.
How should these be treated so they don't rust?
The treatment should withstand lawnmowers (certain wear) and UV light. I don't want to maintain and treat these every year...

I've come across some tips, such as:
- Old motor oil and "burn it in" with a torch.
- Coat with raw linseed oil - put the iron in the oven at the highest possible temperature (275 degrees?) for 1-2 hours.
- Heat the cast iron with a torch (5-600 degrees?) Place the object in a bath with raw linseed oil. A wax-like layer forms as protection.
- Others suggest that rapeseed oil or boiled linseed oil works just as well.
- Then there are advertisements for a number of other special agents...

How sustainable are the above tips?

 

[Dan_Johansson]

If you don't want to do anything, powder coating is the only thing I can think of...

Oil and into the oven is what you do with cast iron pans and they can still rust, especially if you place another pot in it and it's damp underneath...

 

[snuttjulle]

Just a counter-question. Is it for aesthetic reasons or because you think it will rust away that you want it not to rust? There are no street drains that are treated and they last for many years.

 

[Albireo]

Only because it looks nicer if they are not rusty, and to try to test if the method is sustainable. (maintenance-free)

 

[pacman42]

A counter-question. Is it for aesthetic reasons or because you think it will rust away that you don't want it to rust?
There are no manhole covers that are treated and they last for many years.

In particular, manhole covers are replaced quite frequently on the West Coast, they start to clatter (after a few years) because they've shrunk in diameter and thickness. Here, both road salt and sea salt contribute.