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topic 21227

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


A discussion started in 2003 but continuing through 2018

2003

Q. I have removed the paint from a Victorian cast iron fireplace, and burnished it back to a mostly silver finish. I tried sealing it with an ordinary matte varnish and then a high quality acrylic seal I use on the floor, but the varnish/seal seemed to 'rust' and turn brown as soon as I applied it, so I've just left it bare. I now wish to restore another cast iron Victorian fireplace in the same way, but the trouble is, it's in a bathroom, and I'm afraid it will start rusting instantly from steam. Is there any sealer I can use to protect it and stop it rusting, please? (By the way, I read with great interest the letter posted on this website about sealing a restored cast iron oven door with lard, but I really want to avoid this option in my sweet-smelling bathroom!)

Thank you,

Kate [last name deleted for privacy by Editor]
- UK


2004

Q. I have a very similar question: how do I seal a cast iron fireplace that has recently been stripped of paint? I do not want to put the black "Zebo" polish on it, but would like to keep the original cast iron metal look. someone has suggested WD40 oil...could this be right? I know it needs something to protect from oxidation/rusting. many thanks...

Amy H [last name deleted for privacy by Editor]
- London, England, U.K.


Fireplace Styles
from Abe Books

or

2004

A. WD-40 [linked by editor to product info at Amazon]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.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


2005

Q. I have just acquired two late 1800's cast iron fireplaces. They are covered in layers of old paint and was wondering if you could tell me how to go about refinishing them or where I could look to get information on how to do this?
Thanks,

Terrie K Larkins
arts & entertainment productions - Jackson, Tennessee


2005

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.

David Johnson
- Northampton, England, U.K.


2007

Q. I have a old cast fireplace, its black but in places it looks dull and there is rust at the bottom. I was just wondering if there is a blacking or something that I could use to help prevent this happening?

Maureen Copson
hobbyist - United Kingdom


April 21, 2009

A. I have been told to rub on Linseed Oil [linked by editor to product info at Rockler] to protect and finish cast iron

Alan Ewing
- Kirkintilloch, U.K.


July 11, 2010

Q. We have a faux-antique cast-iron mermaid in our back yard that we display on a large rock next to our pond. We are very fond of "Ariel," even though she's quite rusty -- that's part of her charm -- and don't want her to rust away to nothingness. Is there any kind of non-paint product we can apply to her to preserve her current state while retarding further rust?

Ellen Polzien
- Beaverton, Michigan


July 12, 2010

A. Hi, Ellen. The previously mentioned WD-40 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,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


June 16, 2014

Q. I too have bought a rather rusty French cast iron fire and want to rust protect it before using grate polish. Any ideas what to use as a rust protector so that I can put grate polish on after?

Rob Swxton
- Honiton, Devon, UK


A. Hi Rob. I'd say remove the loose rust with a wire brush, apply a rust converter, and then do your grate polish.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


October 19, 2014

Q. I have just bought two large cast iron deer for the garden and they have a wonderful partial rusty look which I want to retain, but also want to protect from further weathering. Can anyone advise what would be the best treatment?

Kay Keesing
- Hythe UK


October 2014

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,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



November 11, 2014

Q. I have a similar question about sealing/finishing cast iron; and very intrigued by and seeking amplification of the earlier response from Ted Mooney. I am wanting to seal a concealed area which can use opaque coatings. Also it will not only be concealed, but basically permanently inaccessible, so the coating needs to be virtually permanent. What I have is a brand new porcelain cast iron sink, but the edge is unfinished so I cannot use it for a tile-in application without somehow finishing the edge. Will this be somehow possible to accomplish? I am thinking the finished edges for tile-in sinks maybe are applied before the porcelain to avoid damage--such as the high heat of powder coating. If there is a practical solution I would be very happy to see it. Thank you.

Mr. Del Mack
- Tucson, Arizona USA


November 2014

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,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


November 12, 2014

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.

Del Mack
- Tucson Arizona USA


November 2014

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,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



December 12, 2015

Q. I am making a 1920 trend new home sewing cabinet into my bathroom vanity. I am looking for the best way to clean up the rust and seal the cast iron from further rusting without losing the old character it currently has.

ila werkmeister
- maywood, nebraska USA



April 9, 2016

Q. I have 80 gallon iron sugar boiler and would like seal it without changing the iron look. Rust is there and soot; convertor turns it black, What is rust arrestor? I saw on a D-I-Y show, This will be a water feature, Others have suggested Crisco, You say clear sealers do not work; thanks for ideas.

Nelson Pollock
- High Point, North Carolina USA


April 2016

Rust Converter

A. Hi Nelson. I think rust arrestor is just another name (possibly covered by trademark) for rust converter. 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 than without, but if you don't like the look, you don't like it :-)

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



Coating an indoor metal art piece for use outdoors?

July 2, 2016

Q. I found the perfect indoor metal wall artwork (ad didn't say what kind of metal) that I would like to put in an outdoor space. The area is protected from rain, but it does get afternoon sun. Is there a coating that I can put on the piece to protect it from the outdoor environment?

Pat Caminiti
Home upgrades - Thousand Oaks, California, USA


Brass Lacquer

July 2016

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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



Old British cast iron park bench ends

August 15, 2016 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hi,

I have a pair of old (possibly Victorian) park bench ends. I think they are cast iron. They are rusty in places, and painted in other areas. The paint is thin and old. Overall I like the patina on the items.

However I'd like them a bit darker, and am wondering about taking them back to the iron. I'm not sure modern paint by hand would look great ... and I don't have many industrial resources to hand.

Are there thin products out there that could achieve a dark look?

Thanks!

Will

Will Paltridge
Hobbyist - UK


August 17, 2016

Birchwood-Casey Gun Bluing

A. Remove the rust with some light sanding with wet/dry paper, then apply a cold blackening agent, like Birchwood Casey Presto Black.

dave wichern
Dave Wichern
Consultant - The Bronx, New York


August 2016

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 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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



March 21, 2018

Q. I've just purchased a cast iron fireplace and am wondering what the hell I'm doing. It was faux marbled so I'm stripping off the paint and coming down to silver in some spots. I thought, well, maybe this isn't cast-iron but did the magnet test and it stuck so I assume it is. Where are the best resources that I could find on how to restore this back to an original black surface and what products I need? There seems to be very little information of this on-line I'm finding.

Thanks

Mike Dooley
- Milwaukee, Wisconsin US



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