Outdoor finish to preserve raw cast iron

[Ali]

I need to fit a couple of these cast iron vent covers outdoors.

The owner likes the look of the raw cast iron.

I’ve tried clear coating steel for outdoors before and found it eventually rusted, perhaps something in my technique or choice of clear coat. I was wondering about epoxy, but this might make it shiny, detracting from the look of it (and messy to undo if not right). Might a soak linseed oil work, and if so for how long? Or just get a metallic cast iron shade paint, and not tell them…

Thanks

 

[Kram]

If the customer is paying, cerakote may be a good option.

 

[oldbikedavey]

Beeswax might be worth a look... Applied to well - warmed metal, it gets right in and stays there, so 'tis said....

 

[Agroshield]

The challenge is not so much in the coating, it is in fitting them so they can be easily removed for periodic maintenance when the coating needs refreshing.

 

[Ali]

Thanks for the suggestions. Cerakote seems a good maintenance free option.

Beeswax might be worth a look... Applied to well - warmed metal, it gets right in and stays there, so 'tis said....

I was thinking with our typical UK summer weather cycle of heat/rain, a wax finish might not be durable outdoors.

The challenge is not so much in the coating, it is in fitting them so they can be easily removed for periodic maintenance when the coating needs refreshing.

They’ll be fitted with an insect mesh and screwed in place with a bead of silicone so not impossible to remove in future.

 

[JOEPRO]

For sure I would powdercoat or paint them in a suitable cast iron like appearance. Leaving them bare with wax etc will never work here!

 

[slim_boy_fat]

Where's @The_Yellow_Ardvark when you need him?

 

[The_Yellow_Ardvark]

De rust. Clean hard with a wire brush. Until the surface is a uniform finish.
No rust or old finish should remain.

Then warm it until spit bubbles. Cast will soak up water like a sponge.
When warm finish with a good clear coat. I tend to give 5 or 6 coats.
Then about 8 coats of bee's wax and warm Linseed oil.

 

[voipio]

Putting it in a gas tight box, and filling the with dry nitrogen, is the only real solution.

Having said that, there are some ceramic glaze finishes which can give a fairly close approximation to fresh cast iron, and might lend themselve to being applied to the cast vent covers. They may not be all that durable, but might survive if not knocked too hard. Page 8 of this free book might show a way of doing this. There's some interesting info in there, too:

https://ceramicartsnetwork.org/docs/default-source/uploadedfiles/wp-content/uploads/2008/04/33triedtrueglazes.pdf

 

[Gareth J]

"They" the people from history, used to use bitumen, once it was available. Often find it oozing out when you heat up an old cast outdoor thing. Not the best performing of coatings in many ways but will soak in well, weather sympathetically and is easy to recoat.

Hot dip galvanise them and paint in a castish colour is probably the best option for no rust. But the the paint will peel and it'll look worse than a rusty one!

 

[Hitch]

I do a few coats of matt black, followed by a couple of generous coats of iron paste.

 

[steve t]

Hot dip galvanise them and paint in a castish colour is probably the best option for no rust. But the the paint will peel and it'll look worse than a rusty one!

cast iron doesn't take galvanising well.

 

[Ali]

De rust. Clean hard with a wire brush. Until the surface is a uniform finish.
No rust or old finish should remain.

Then warm it until spit bubbles. Cast will soak up water like a sponge.
When warm finish with a good clear coat. I tend to give 5 or 6 coats.
Then about 8 coats of bee's wax and warm Linseed oil.

Any particular clear coat?

 

[Kram]

Do not powder coat, wont last 5 minutes on a part like that. One small chip and it will all flake off.

Another option is to copper electroplate it with copper sulphate. Would look quite good I think once it has a good green copper patina. It is quite easy and cheap to do, but a slow process for good results. Alternative is then to zinc plate and bake it, to get a brass appearance.

Where are these used? I assume some kind of garden feature/building.

 

[Ali]

Do not powder coat, wont last 5 minutes on a part like that. One small chip and it will all flake off.

Another option is to copper electroplate it with copper sulphate. Would look quite good I think once it has a good green copper patina. It is quite easy and cheap to do, but a slow process for good results. Alternative is then to zinc plate and bake it, to get a brass appearance.

Where are these used? I assume some kind of garden feature/building.

Replacing these

 

[Kram]

Oh then they are much smaller than the original pic had me believe I imagined that was a meter or so wide.

Ignore my suggestion about a green copper patina, that would be awful on the side of a white house Brass would still look ok though.

 

[Ali]

Oh then they are much smaller than the original pic had me believe I imagined that was a meter or so wide.

Sorry, didn’t have a banana available at time of photographing

 

[MetalMonkey]

Speaking as someone with a Victorian house with a fair amount of original cast ironmongery I can say the "traditional" approach appears to have been four billion layers of thick black leaded gloss paint.
Take from that what you will.

 

[The_Yellow_Ardvark]

Any particular clear coat?

I do like the Clear lacquer from Holt.

 

[Kram]

Any particular clear coat?

I have some Upol S2085 spare if thats any interest. I believe its one of the better 1k clear coats. This stuff:

U-POL 1K Acrylic Smart Clear (S2085/1) | Spray Guns Direct

U-POL S2085/5 is a HS 1K Acrylic Clearcoat, it can be applied un-thinned or thinned up to 10% with thinners. Rapid UK and Global Shipping.

www.spraygunsdirect.co.uk