Remove Rust and Seal Cast Iron Fireplaces, Mermaid & Reindeer Yard Art

A. WD-40 can probably be very helpful indeed, but this is not a one-time application like painting, it's a constant reapplication.

The thing is, iron and steel rust very quickly; that's their nature and one of the major reasons painting and plating and other surface coatings are used. Further, for a protective coating to work well requires an application process that includes opaque pretreatments like phosphatizing to add "key" to the surface, to minimize anodic hot spots, to deter rust in scratched areas, etc.

When someone polishes iron, leaving the highly reactive metallic surface, and they don't want to pretreat with an opaque material, but just want to "clearcoat" it, everything is working against them. There may well be clearcoats that are better than the one you tried, but there is no way to truly protect a shiny steel surface right and well with only a clearcoat -- the best you can hope for is 'good enough' for use indoors and not in a kitchen or bathroom.

A. Yep I've cleaned up a few 1880's cast fireplaces and after stripping the paint and goo off with a round wire brush in a drill and paint stripper I liked the look of the raw grey/black cast, so I did the following, Do not wash with water but rub down with fine wire wool, move to a well ventilated area and spray well with a few coats of a non-flammable hair spray to seal out any dampness. Still looks good, no probs.

A. I have been told to rub on boiled linseed oil ⇦this on eBay or Amazon [affil links] to protect and finish cast iron

A. Hi, Ellen. The previously mentioned WD-40 ⇦this on eBay or Amazon [affil links] or linseed oil should work fine for Ariel as well. A simple clear coat like Everbrite [a finishing.com supporting advertiser] should be fine, too. But beauty is in the eye of the beholder, so try these things on an inconspicuous spot first to make sure any change they may make doesn't affect her charm.

Regards,

A. Hi Rob. I'd say remove the loose rust with a wire brush, apply a rust converter ⇦this on eBay or Amazon [affil links] , and then do your grate polish.

Regards,

A. Hi Kay. Put them in a glass museum case :-)

Seriously, there is no great answer because the rust does not adhere well to the cast iron, so even if the clear coat adheres well to the rust, you still have poor adhesion. Secondly, a clearcoat is not much protection from continuing rust, and thirdly the clearcoat will build up and start looking ugly after several coats. I would try the thin single-component clearcoats like Everbrite [a finishing.com supporting advertiser] and re-do it every year or two.

The hope would be to seriously slow down the rusting, not to stop it in its tracks. Good luck.

Regards,

A. Hello Del. I'm no home remodeling guru, so I'm not even quite picturing your "finished edge for tile-in sinks". This is a vertical surface, flush with the tile line, and sealed with caulk or grout? I did not say that cast iron can't be finished, I said that trying to seal a rusty surface onto cast iron with clearcoat is a problem because rust is loose and non-adherent ... and further, that a layer of clearcoat is very little protection against ongoing corrosion, especially in outdoors exposure.

Maybe try Ospho or naval jelly followed by a primer.

But I don't understand your reference to porcelaining before powder coating; porcelain enamel is a much higher temperature process than powder coating -- basically glass-melting temperature rather than plastic-melting temperature.

Regards,

Q. Yes, I understood about the insufficiency of a clear coat, and I have a brand new sink, so there is no rust at this point. And yes, the sink has a vertical, but slightly rounded edge to face the tile edge, with the small gap between to be grouted in. The issue lies in waterproofing the exposed, unfinished sink edge and a portion of the under surface trailing away from the edge back toward the center of the sink. Tile in sinks have a special hardened finish edge, but Kohler does not make a tile in model for bath vanities. If I cannot permanently seal this area with some kind of finish process, I will definitely get rusting around that edge. My powder coat comment came from speaking with a shop that does powder coating, and was told the furnace heat would likely crack the porcelain surface. Your comment about that revives a hope I might just have that portion of the cast iron bowl powder coated, if that would provide a more or less permanent water seal? or are there other sealers which could be applied to finish that edge against water exposure?
Thanks.

A. Hi again. Sorry, I don't know enough about the porcelain enamel on a sink to guarantee that powder coating temperatures won't cause it to crack. I would think not, but I don't know.

Still, while powder coating is a good finish, it's not some miracle finish; it's an application method more than a type of coating. It doesn't do anything corrosion-wise that you can't do with wet paints. I would apply the Ospho or naval jelly -- which is the closest you can do at home to achieve a phosphate finish -- (or send it to the powder coater just for pretreatment, not powder coating), then two coats of paint, i.e., a purpose-made primer, followed by either another coat of primer or a finish coat. And I'd use silicone caulk or careful grouting to try to keep it dry. Good luck.

Regards,

A. Hi Nelson. I think rust arrestor is just another name (possibly covered by trademark) for rust converter ⇦this on eBay or Amazon [affil links] . I'm not familiar with the Crisco idea, but would guess that they were talking about "seasoning" the cast iron with Crisco and heat.

I don't think anyone said clear sealers "don't work". But I think we did introduce two issues to be wary of:
1. Clearcoats are probably not enough protection for bare steel or iron, particularly for an outdoor water feature. It's not the clearcoat on an automobile that prevents rust, it's the galvanneal zinc coating, followed by phosphatizing, followed by electrophoretic priming, followed by the color coats, followed by the clear coat -- a whole system of 6 or more layers.
2. If you want to retain the look of loose, dusty, non-adherent, powdery rust, a problem is that it just brushes off; and clear coats are not shrink wrap, and will to some extent come off with the rust.

I think you need to wire brush any loose rust off to try to minimize the problem. You'd have a better fix with rust converter ⇦this on eBay or Amazon [affil links] than without, but if you don't like the look, you don't like it :-)

Regards,

Brass Lacquers

on eBay or

Amazon

(affil links)

A. Hi Pat. You can probably successfully apply brass lacquer or just spray with polyurethane. If the ads or label say "non-yellowing" or "UV Protection", it is more likely to withstand the sun.

While it will probably be fine, "metal art piece" is so broad that no one can guarantee that you won't have problems. It's easy to picture cardboard decorations on the item, paint that will peel in the heat of the sun, and so on. And, at best, such coatings are usually only good for a few years before recoating is necessary. Good luck.

Regards,

A. Remove the rust with some light sanding with wet/dry paper, then apply a cold blackening agent, like Birchwood Casey Presto Black ⇦this on Amazon [affil links] .

A. Hi. While I think Dave's suggestion will darken the cast iron, I don't think it will hold up outdoors; blackened firearms are lovingly maintained including cleaning, drying, and oiling. I'd probably suggest a rust converter ⇦this on eBay or Amazon [affil links] followed by clear coating with Krylon or something similar. Even then, assuming the bench is outdoors, the clear coating will have to be re-done every year or three depending on environment. Good luck.

Regards,