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Old 04-29-2012, 04:06 PM   #1
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Painting a Clawfoot Bathtub


I need advice on painting the exterior of a clawfoot bathtub. The exterior of the tub was blasted with crushed glass (soda blasted on the interior) and all of the old paint was removed with this process. The cast iron has some pitting, probably due to age and years of sitting outdoors, but the blasting cleaned it up nicely.

The same day, we rubbed it down with denatured alcohol and then painted it. First we sprayed it was two coats of Rust-o-leum Professional Primer. We were careful to follow all of the manufacturer's instructions and the weather conditions for spraying (the tub was outside on a trailer) were within the parameters specified. We then sprayed the tub with two coats of Rust-o-leum Hammered metal paint. We picked this because the color and the textured would look the best of any of the Rust-o-leum paints available. Again we were careful to follow the manufacturers instructions. This was done about 1 1/2 week ago.

The tub has remained outside and it has been rained on a few times since it was painted. We now starting to see rust showing through where there is pitting along the sides. The top coat of paint has not hardened to the point where it cannot be scratched off with a fingernail.

We plan to strip the paint and redo it, but this time I want to be sure that I'm using a paint which will not allow the metal to rust. Eventually the tub will be moved into the house, but since a bathroom is a moist environment I need to be sure that the paint can withstand the humidity. I know I could spend a bunch of money and have the whole tub urethaned by professionals, but the whole point of using this tub was to save money by doing the project ourselves. I'm not concerned about the interior of the tub; it's got some stain but it's fully serviceable as it is. I am however concerned about the exterior. I want a good durable paint that will last for years to come.

Any suggestions? Thank you in advance for your replies.


Last edited by techinstructor; 04-29-2012 at 04:07 PM. Reason: remove line breaks
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Old 04-29-2012, 04:13 PM   #2
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Painting a Clawfoot Bathtub


Benjamin Moore Oil base Impervo for the finish coat. It is an oil solvent based product but great stuff.

Ask your real paint store what to use as primer depending on how deep you want to get to the original surface.

Alkyd primers are the great problem solvers/problem preventors.

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Old 04-29-2012, 04:40 PM   #3
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Painting a Clawfoot Bathtub


Pretty much agree with sds- but I have had great success priming things like radiators with bare metal showing with zinsser 123. It is a metal primer- dries fast and seals it . do 2 coats.
The finish with oil imp is a very good idea.

you will bring this inside, right? or is it a cowboy tub?? lol

Cover it and keep the rain off while it cures!
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Old 04-29-2012, 04:44 PM   #4
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Painting a Clawfoot Bathtub


Imron or Awlgrip.
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Old 04-29-2012, 09:16 PM   #5
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Painting a Clawfoot Bathtub


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Originally Posted by Brushjockey View Post
you will bring this inside, right? or is it a cowboy tub?? lol
You think you are so funny? Well Ok, you caught me off guard.

Seriously? And I have hinted before I cheat and drag things I am not really sure how to paint to my local auto body shop. Furniture for babies I find at antique shops and all sorts of stuff. We who painted walls and ceilings forget we have kindred brothers and sister, with really nice spray equipment and all hidden so close to us.

Obviously moving your tub, full of water and cowboys and one supposes cowgals will be heavy. I would drain the water and deal with the soap scum ring.

If it needs any degree of restoration? Your autobody shop will know how to handle it. And please trust me. A clawfoot tub will move to the top of the list their employees want to work on faster than a 10 speed Lamborghini with a ding in the fender. The guys get bored doing usual bondo car work.

The owner of the shop near me knows something weird is going to be asked of his place when I come near. Guys and girls with masks and aspirators appear from nowhere and see what I have brought and say cool. "Let's make room for this project and dump the Jag in the Chicago River."

Of course I never pay them. They live under an umbrella of pure glory.

Last edited by user1007; 04-29-2012 at 09:34 PM.
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Old 04-29-2012, 09:56 PM   #6
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Painting a Clawfoot Bathtub


Quote:
Originally Posted by techinstructor View Post
I need advice on painting the exterior of a clawfoot bathtub. The exterior of the tub was blasted with crushed glass (soda blasted on the interior) and all of the old paint was removed with this process. The cast iron has some pitting, probably due to age and years of sitting outdoors, but the blasting cleaned it up nicely.

The same day, we rubbed it down with denatured alcohol and then painted it. First we sprayed it was two coats of Rust-o-leum Professional Primer. We were careful to follow all of the manufacturer's instructions and the weather conditions for spraying (the tub was outside on a trailer) were within the parameters specified. We then sprayed the tub with two coats of Rust-o-leum Hammered metal paint. We picked this because the color and the textured would look the best of any of the Rust-o-leum paints available. Again we were careful to follow the manufacturers instructions. This was done about 1 1/2 week ago.

The tub has remained outside and it has been rained on a few times since it was painted. We now starting to see rust showing through where there is pitting along the sides. The top coat of paint has not hardened to the point where it cannot be scratched off with a fingernail.

We plan to strip the paint and redo it, but this time I want to be sure that I'm using a paint which will not allow the metal to rust. Eventually the tub will be moved into the house, but since a bathroom is a moist environment I need to be sure that the paint can withstand the humidity. I know I could spend a bunch of money and have the whole tub urethaned by professionals, but the whole point of using this tub was to save money by doing the project ourselves. I'm not concerned about the interior of the tub; it's got some stain but it's fully serviceable as it is. I am however concerned about the exterior. I want a good durable paint that will last for years to come.

Any suggestions? Thank you in advance for your replies.
Hiya Tech...

Sounds like you gotta couple of problems there...(1) rust pitting through 2 coats of primer and 2 coats of finish - and (2) the final application of finish not curing properly.

First, if rust is coming through that many apps of primer and paint, your problem must be in the prime coat. You said this was a Rustoleum Professional Primer - alkyd or latex? By blasting with glass removed all the old paint, did it remove all the rust also? If so, had any flash rusting occurred before applying primer? Typically, when rusting occurs in the manner you've described (and especially through that many coats of product), you've probably entrapped air (or moisture) in the pits of the tub...Oil based Rustoleum (which makes very good products, btw), generally penetrates the surface very well and coats the multi-faceted surface of pitted steel enough to effectively retard further oxidation. A second coat of the same primer should then provide adequate film thickness necessary to bury, or encapsulate any remaining protrusions that may "peak" through a single app of primer. Latex Rustoleum is great for clean metal, not so great on rusty metal (including flash rusting). So...by spraying it, how much did you ultimately thin the product, and do you know how much mil thickness you achieved, per coat?

Second, Rustoleum Hammered Finish is a really good product. Not only is it rust-inhibitive, it can also be applied directly to tightly adhering rust without the use of a primer (that's not often true with most rust-inhibiting finishes...nor, rust-inhibiting primers for that matter). The one thing about Hammered Finish is their very short window for re-coating - after 30 minutes and before 4 hours. If after 4 hours, wait a week or so...Personally, my experience with spraying Hammered Finish has been excellent, but I don't think I'd try re-coating that product (especially when sprayed) after only 30 minutes - I'd wait at least a couple of hours. Why? Because in less than controlled conditions, there's too good of a chance of entrapping solvent that would keep the finish from curing properly - which effects hardness and adhesion. Again, what did you thin the product with to spray, and how much? (Xylene is the only recommended thinner)...and what was your re-coat time?

Last question - did you use any type of rust "converter"?

Depending on what type of Rustoleum Professional Primer you used, what you've described is a very good rust inhibiting system. A urethane coating wouldn't necessarily provide any better protection from rust. Rusting could only take place if moisture, or air, was entrapped by the film(s) - or steel protrusions were not entirely encapsulated, causing a break in the film and allowing exposure to air (actually oxygen molecules). The finish coat's ability to cure may be derailed by atmospheric conditions (including surface and material temps), improper thinning amounts or solvent types, too heavy an application, a second coat applied too soon, etc.

I wouldn't be too quick to blame the paint...but I definitely wouldn't change to a different brand or system before I could determine the specific cause of what went wrong with the Rustoleum system.
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Old 04-30-2012, 09:59 AM   #7
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Painting a Clawfoot Bathtub


sdsester and Brushjockey... Thanks for the recommendations for Impervo and Zinnser 123. I've looked up the specs on both and they seem like they fit the bill. However I'm more concerned about prepping the substrate after reading the post from ric knows paint.

And yes, we do plan to bring the tub inside. (I've bathed in a "cowboy" tub before but indoor tubs are much nicer. ) It's a bit heavy and we were waiting on forks that we ordered for our tractor, so we can put it on a pallet and lift it through the porch posts to a position right in front of the door. The feet are not currently on it and we didn't want to risk messing up the paint if we should need to put it down and rest while carrying it. Actually, I'm glad we discovered the rust now before we set it up in the bathroom.

CaptRandy, I'll check out your recommendations as well. Thanks.

Last edited by techinstructor; 04-30-2012 at 10:51 AM.
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Old 04-30-2012, 10:50 AM   #8
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Painting a Clawfoot Bathtub


Quote:
Originally Posted by ric knows paint View Post
Hiya Tech...

Sounds like you gotta couple of problems there...(1) rust pitting through 2 coats of primer and 2 coats of finish - and (2) the final application of finish not curing properly.

First, if rust is coming through that many apps of primer and paint, your problem must be in the prime coat. You said this was a Rustoleum Professional Primer - alkyd or latex?
It was in a rattle can -- alkyd primer.

Quote:
By blasting with glass removed all the old paint, did it remove all the rust also? If so, had any flash rusting occurred before applying primer?
There was no "flash rusting" if by that you mean a thin layer of rust forming on the surface. There may have been some very small amount of rust still down in the pits, but the metal looked clean after blasting.

Quote:
Typically, when rusting occurs in the manner you've described (and especially through that many coats of product),you've probably entrapped air (or moisture) in the pits of the tub...Oil based Rustoleum (which makes very good products, btw), generally penetrates the surface very well and coats the multi-faceted surface of pitted steel enough to effectively retard further oxidation. A second coat of the same primer should then provide adequate film thickness necessary to bury, or encapsulate any remaining protrusions that may "peak" through a single app of primer. Latex Rustoleum is great for clean metal, not so great on rusty metal (including flash rusting). So...by spraying it, how much did you ultimately thin the product, and do you know how much mil thickness you achieved, per coat?
My husband did the spraying and I have no idea how to estimate just how thick it was. The instructions said to apply "2 or more light coats a few minutes apart" He applied a thin coat with even coverage, so that the metal did not show through. When the whole tub was done, he did the second coat.

Quote:
Second, Rustoleum Hammered Finish is a really good product. Not only is it rust-inhibitive, it can also be applied directly to tightly adhering rust without the use of a primer (that's not often true with most rust-inhibiting finishes...nor, rust-inhibiting primers for that matter). The one thing about Hammered Finish is their very short window for re-coating - after 30 minutes and before 4 hours. If after 4 hours, wait a week or so...Personally, my experience with spraying Hammered Finish has been excellent, but I don't think I'd try re-coating that product (especially when sprayed) after only 30 minutes - I'd wait at least a couple of hours. Why? Because in less than controlled conditions, there's too good of a chance of entrapping solvent that would keep the finish from curing properly - which effects hardness and adhesion. Again, what did you thin the product with to spray, and how much? (Xylene is the only recommended thinner)...and what was your re-coat time?
Again, we used Hammered Rust-o-leum in the rattle can. The primer can said that topcoats can be applied immediately, so that is what we did. The instructions for the Hammered said to recoat within one hour or 48 hours. Since we knew we were leaving it outside, we recoated as soon as the first coat was done. So basically, we applied the four layers (2 primer, 2 hammered) in succession, one after the other.

Quote:
Last question - did you use any type of rust "converter"?
I don't know what this is, so the answer is no. Should I have used this?

Quote:
Depending on what type of Rustoleum Professional Primer you used, what you've described is a very good rust inhibiting system. A urethane coating wouldn't necessarily provide any better protection from rust. Rusting could only take place if moisture, or air, was entrapped by the film(s) - or steel protrusions were not entirely encapsulated, causing a break in the film and allowing exposure to air (actually oxygen molecules).
Sounds like this was the problem. I'm really glad to hear that the product we used was good because I loved the way it looked. The textured sheen of the hammered paint blended well with the less-than-smooth surface of the old cast iron. We used a medium brown color and it came out looking sort of like oil rubbed bronze. It also match my beige tile really well.

Quote:
The finish coat's ability to cure may be derailed by atmospheric conditions (including surface and material temps), improper thinning amounts or solvent types, too heavy an application, a second coat applied too soon, etc.
It did get below 50 degrees the night we painted it and then it rained a day or two after that. Maybe covering it to keep the rain off would have helped with this.

In light of this information I'm wondering about how to remedy the problem. I really hate to have to strip the paint and start over. We have enough of the primer and hammered to repaint, but I'd be interested in suggestions as to how we should prepare the surface.

Do you think it is necessary to strip the paint down to the metal because of the encapsulated air?

Given time, and warmer temperatures, will the paint topcoat eventually harden?

It would be so easy if we could just wipe off the rust and repaint with topcoat but I'm unsure as to how effective this would be.

Thank you so much for the information. I'm learning a lot!

Last edited by techinstructor; 04-30-2012 at 10:52 AM.
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Old 04-30-2012, 11:47 AM   #9
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Painting a Clawfoot Bathtub


OK, typically I made the wrong assumption - and that changes a few things, but not everything...I was assuming you were using the quart cans of prime and hammered finish and spraying through airless or HVLP...what you thinned with is obviously no longer an issue...However,

Aerosol sprays are fine for priming bare steel - they are essentially the same compositional make up as their brushable counter-parts are - except at a lower solids content and typically much faster dry (than brushable). Sometimes that presents a couple of problems, and you may have encountered both. The first problem is, since it's a lower solids product, it doesn't have the ability to penetrate into the crevices of pitted steel and still provide a uniform protective film, nor the mil thickness (depth) to fully encapsulate surface irregularities...Second, the solvent structure is often times altered from brush-on to aerosol. This change of solvent probably limits the mfr. from using the same type of oils found in the brush version. Rustoleum used to extend their alkyd primers with fish oil (and other slower, or non-drying oils) to allow for deep penetration into the microscopic crags and crevices found in pitted steel. This slow drying, deep penetrating component also allowed the oils to "wick" up and surround (encapsulate) the odd shaped (multi-faceted) protrusions to prevent further oxidation. While effective, these primers usually required minimum overnight dry before finishing, and sometimes 24 - 48 hours (side note: I don't know if Rustoleum still uses fish oils (or similar), but I think it'd be difficult to mix slow dry oils with the often lower flash solvents found in aerosols).

The same idea is most likely true with aerosolized Hammered Finish. There may simply have been not enough mil thickness to fully envelop any surface protrusions, which allowed rusting to continue.

As far as a rust converter goes - No, it wouldn't have been necessary to use a rust converter, and personally I'd rather see someone remove rust than to convert it to a "paintable" surface by using converters. The reason I asked is there are some water-based converters on the market that require iron oxide to catalyze. Without the iron oxide, the converter remains on the surface, uncured and gummy, which could wreak havoc on any subsequent coats of prime or finish.

And, finally, I don't thinks it's gonna be necessary to remove everything you've done and start over. I can't answer your question whether the soft coating will eventually cure hard - probably. Wipe it down with Xylene and see what happens. If it removes the soft coating, it probably needed to be removed. If it only dulls the surface, you're probably good to let it set a few more days, then apply another coat over it.

As far as the rusting goes, it sounds like you've got a reasonably good foundation there, but may need a little tweaking at this point. If we're just talking about pin-hole rusting, I'd feel pretty comfortable with wiping it down with solvent (xylene), then recoating with the Hammered Finish...If the rusting is actually interfering with adhesion, I'd wire brush those areas to clean metal, then re-apply prime. At that point, you may want to consider going over the entire surface with another full application of the Hammered Finish (although, I'd recommend buying the quart and brushing the finish on).

I've used Hammered Finish on several different projects (usually sprayed through HVLP) and am always satisfied. I've even used it where Rustoleum recommends not to (aluminum boats and boat motors) with excellent results. I think you're OK...sorry this is so long-winded and hope it's more informative than confusing. Good luck.

Last edited by ric knows paint; 04-30-2012 at 04:54 PM.
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Old 04-30-2012, 01:03 PM   #10
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Painting a Clawfoot Bathtub


I have an old cast iron tub where a dripping faucet over the years wore away the porcelain and there was a round rusty spot on the bottom of the tub. I painted the spot with a white two part epoxy paint. The faucet has been repaired but the painted spot has held up with the tub in use. This type of paint is available in marine supply stores and might be a solution to the problem.
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Old 04-30-2012, 05:57 PM   #11
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Painting a Clawfoot Bathtub


Ric knows paint.... Thank you so much for your explanations. You're not long-winded and the details really help me to understand what went wrong and hopefully how to fix the problem. We're going to try wiping it with Xylene and repainting. Lowes didn't have any Xylene or the Hammered Brown in non-aerosol Hammered so I have to try to find it at the paint store when they open tomorrow. I'll let you know how it turns out.

Again, thank you for all the information. It is truly appreciated!

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