# Epoxy Paint vs Oil-Based Metal Paint



## Einhorn (Jun 12, 2011)

I have a condo management firm and typically we contract all work out. A few years ago we contracted the re-painting of exterior metal railings to a painter who specified that they would remove loose rust, and then prime and paint with rust-paint. The rust later returned within a year.

This year, I’ve discussed the subject with many others, who convinced me that the way to go is the use of a “rust converter”. The brand ‘Qurox’ was recommended although the idea as I understand it is relatively standard…an organic acid (usually tannic acid) mixed with a co-polymer, and the combination reverses the oxidization and seals the metal, acting as a primer.

The manufacturer of Qurox recommends scraping/grinding loose ruse off, then applying 3 thin coats of Qurox, with an hour to dry between each coat. Although they are not in the paint business, he recommended that we complete the job with 1 coat of Epoxy paint.

Our painting contractor (different person from prior years) agrees with all of this, expect for the Exoxy paint. He commented that Epoxy paint is excellent, but is also very expensive and he didn’t see the benefit from the added expense, especially in light of 3 coats of Rust converter. 

We’re in Canada, where Oil-based paints will be largely removed from the market by next Year. Our painting contractor recommends using as much Oil based paint while we still can.

He didn’t mention this, but one possible consideration is that the original paint (7 years ago) is oil-based paint. Since we won’t be stripping, and the only primer will be the rust-converter, is it fair to say that Oil-based would work better? And if we were to move to epoxy paint, we would either need to strip the existing oil-based paint, or prime it with something in addition to the rust converter?

A final consideration, I read that Epoxy paints, while strong, don’t hold up well to Ultra-Violet radiation. These metal railings get a lot of sun.

Thanks for any suggestions.


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## TJ Paint (Jun 18, 2009)

epoxy and sun don't mix.

You want a urethane system. Its going to cost you.


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## hammerheart14 (May 29, 2010)

I would sand down anything flaking and rusting , feather it out, clean the surface. After that use a good quality rust inhibitive primer, then two coats of a industrial enamel in either semi gloss or gloss. In most cases, acrylic industrial coating will only be available. BUT, if you can get it, get the oil based version of RUST DESTROYER for the prime coat, then use RUSTOLEUM'S HAMMERITE FINISH. GOOD RESULTS with that combo.


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## DeanV (Apr 18, 2007)

I am specifying this http://www.benjaminmoore.com:80/bmpsweb/DownloadBinary?fileName=TDS_M45-M46en.pdf&nodeId=BEA+Repository%2F16351&propertyId=BEA+Repository%2F16351%2Fdata_sheet_file_en_US

For some heavily rusted exterior support poles. I plan to treat with rust converter, one coat, and two coats of this. I find oil based DTM antirust coatings are okay, but do not hold back rush for long in most cases.


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## Einhorn (Jun 12, 2011)

Thanks for the reply.

I understand why Epoxy would be out of the picture if it doesn't like UV.

But what's the issue then with standard oil-based metal paint, if oil-based paint is still available? I've seen that it holds up well over many years if the metal is properly prepared.

When you say a urethane system is "gonna cost me", whats a rough multiple...ie roughly 2x the cost or regular oil-based metal paint, or is it 10x the cost?

Thanks again.


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## hammerheart14 (May 29, 2010)

Einhorn said:


> Thanks for the reply.
> 
> I understand why Epoxy would be out of the picture if it doesn't like UV.
> 
> ...


you don't want oil based paint, you want an oil based INDUSTRIAL ENAMEL! Some industrial coating have a urethane modified coating, which is just a "step" up from regular industrial coatings.


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## hammerheart14 (May 29, 2010)

DeanV said:


> I am specifying this http://www.benjaminmoore.com:80/bmpsweb/DownloadBinary?fileName=TDS_M45-M46en.pdf&nodeId=BEA+Repository%2F16351&propertyId=BEA+Repository%2F16351%2Fdata_sheet_file_en_US
> 
> For some heavily rusted exterior support poles. I plan to treat with rust converter, one coat, and two coats of this. I find oil based DTM antirust coatings are okay, but do not hold back rush for long in most cases.


this product is basically the same as a DTM. Here's what I would use over a good quality rust inhibitive primer:http://www.prattandlambert.com/pdf/product-data-sheets/6610.pdf. 

primer: http://www.prattandlambert.com/pdf/product-data-sheets/6630.pdf


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## pacificpainters.com (May 5, 2011)

*Maintainance system*

First thing that should be established, there is no such thing as a rust converter and no evidence that any of these converters do anything more then change the colour of the rust.

Second, if you have rust it means that the anodic elements of the metal have started to oxidise and react to the cathodic elements within the metal. There is no stopping it now, the best thing is to avoid the metal from starting this process but ounce it starts that's it. the metal WILL corrode and you can only slow it now.

Epoxy is the worst thing you can do because it is such a touch coating the corrosion will occur under the paint and it won't be until the paint cracks apart that you will know that it is corroding again.

The solution is a two fold maintenance system, first a cathodic protection of a sacrificial coating such as Zinc. It is imperative that you first remove most of the rust if not all the rust. But do not use rust converter as it will create a for the cathodic protection.

The next process is anodic passaviation, this can be achieved by using 100% acrylic exterior membrane paint to a dry film thickness of 35 microns. this will prevent or at least slow down the ionic environment from accelerating the electrolysis. It is also a good system for inspection of the substrate and maintenance. Every year spot prime the corrosion with Zinc primer and re coat with the acrylic again.


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## Einhorn (Jun 12, 2011)

I really appreciate your patience. If I could just clarify a bit...you said that "you don't want oil based paint, you want an oil based INDUSTRIAL ENAMEL!". But in your next post you linked to this product:
http://www.prattandlambert.com/pdf/product-data-sheets/6610.pdf

and at that link, the product is described as "a water based 100% acrylic". 

One another point, one given is the rust converter because this has already been purchased. Looking on the bottle of Qurox, it states, "for maximum protection, a solvent based top coat must be used. Do not use water based paint to top coat".

Given this constraint, that we want to use this rust converter/primer, which paint would you recommend?

Thanks again


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## Mike's QP (Jun 12, 2008)

pacificpainters.com said:


> The solution is a two fold maintenance system, first a cathodic protection of a sacrificial coating such as Zinc. It is imperative that you first remove most of the rust if not all


 Correct

wire wheel rust, sand with 80 grit sand paper, wipe with xylene, apply zinc, apply finish coat


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## MonPeintre.ca (Feb 17, 2011)

Metal railling and staircase is about 1/3 of our business. We grind and sand the rust and we spot prime with a red oxyde primer. Is it usefull to prime every surface even if it wasnt damage???


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## MonPeintre.ca (Feb 17, 2011)

I'm not sure if red oxyde is a good product? What do you think?


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## Einhorn (Jun 12, 2011)

What would be a good pain to use on top of a rust converter/primer that specifies "for maximum protection, a solvent based top coat must be used. Do not use water based paint to top coat".


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## DeanV (Apr 18, 2007)

Rust converter bleeds through non oil paints. This is not visible on black but is on lighter colors. A DTM oil is fine over converter.

For zinc, I am not sure zinc will work well on already coated metal, but really not my area of expertise. Wihout zinc contacting the iron it will do very little I think.


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## acmasterpainter (May 15, 2011)

If you could shot blast the railings to bare you might be in to something, zinc it then carry on from there, otherwise, it is a losing battle. On marine metal fittings I blasted and cold zinced the steel, etch primer, chlorinated rubber based mid coat, then 3 coats oil based marine enamel - that did it. Only parts that "failed" were 2 spots where constant rubbing of an anchor chain went down to etch coat.

Also, thickness of paint plays its part in holding back rust. It may well be rusting like a good un underneath, but with plenty of layers to hide evidence at least you feel you beat it.


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## pacificpainters.com (May 5, 2011)

Einhorn said:


> I really appreciate your patience. If I could just clarify a bit...you said that "you don't want oil based paint, you want an oil based INDUSTRIAL ENAMEL!". But in your next post you linked to this product:
> http://www.prattandlambert.com/pdf/product-data-sheets/6610.pdf
> 
> and at that link, the product is described as "a water based 100% acrylic".
> ...


I really strongly recommend that you get rid of the rust converter. Stick with science not gimmicks. 1) remove all rust 2) cathodic protection using Zinc 3) Anodic pasavation using a coating system (I Recommend a 100% acrylic) that can be serviced annularly and does not hide corrosion.


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## pacificpainters.com (May 5, 2011)

DeanV said:


> Rust converter bleeds through non oil paints. This is not visible on black but is on lighter colors. A DTM oil is fine over converter.
> 
> For zinc, I am not sure zinc will work well on already coated metal, but really not my area of expertise. Wihout zinc contacting the iron it will do very little I think.


True Dean, I should have mentioned that. I assumed that the old paint would be removed, if the old paint can't be completely removed then remove the paint around the corroded area and spot prime with zinc.


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## Einhorn (Jun 12, 2011)

To P&D, thank you for your advice. I do appreciate it and I'm not trying to be difficult...but the thing is that the rust converter was already purchased, and partially applied. Now that I have your advice I'll know better in future. But for now, I don't believe its practical to remove the rust converter that's just been applied, toss $1000 of the stuff out, and begin with a different, albeit superior method.

So the question is, after fully admitting the error of my ways for buying rust converter, what would be a good paint to put on top of it, that is solvent based.

Thanks again to anyone for your suggestions.


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## pacificpainters.com (May 5, 2011)

I empathize with your predicament. Sorry for being so tactless and opinionated, it is an Australian thing. 

There are many products available and all solvent based products will be hard wearing but wont be thermosetting which means that the coating will eventually have very fine microscopic cracks that will allow moisture and salts to get to the surface. Someone mentioned hammertone paints before. These are great and they have a silica to repel moisture as well, they are easy to use and easy to maintain. 

Hammertone can be applied over the "rust converter."

As I said it has to be viewed as a maintenance system, hammertone is easy to reapply and maintain.


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## hammerheart14 (May 29, 2010)

Einhorn said:


> I really appreciate your patience. If I could just clarify a bit...you said that "you don't want oil based paint, you want an oil based INDUSTRIAL ENAMEL!". But in your next post you linked to this product:
> http://www.prattandlambert.com/pdf/product-data-sheets/6610.pdf
> 
> and at that link, the product is described as "a water based 100% acrylic".
> ...


Well, to clarify, the oil based rust destroyer was bar none, the best metal primer I have ever sold, used, ect. SO, if you COULD GET THAT, then yes, use an oil based industrial enamel to go on top. BUT if you can't get te hoil based rust destroyer, then you have no choice but to go with the water based products. AS FAR AS THE FINISHES GO, I TRULY BELIEVE that the newer water based industrial enamels are just as good as the old oils, but i DO believe that the oil based rust destroyer (metal primer) was and is untouchable. Did I clarify myself?


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## hammerheart14 (May 29, 2010)

Einhorn said:


> I really appreciate your patience. If I could just clarify a bit...you said that "you don't want oil based paint, you want an oil based INDUSTRIAL ENAMEL!". But in your next post you linked to this product:
> http://www.prattandlambert.com/pdf/product-data-sheets/6610.pdf
> 
> and at that link, the product is described as "a water based 100% acrylic".
> ...


Ok, for second question, you used an oil based rust converter primer. STICK with an oil based industrial enamel, like the Hammerite I mentioned, by masterchem (same people who makes kilz) i don't know the laws in your state, but in so cal, we can only buy quarts of it. Check your local paint store, but IF YOU USED AN OIL BASED PRIMER, STICK WITH AN OIL BASED INDUSTRIAL FINISH.


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## Einhorn (Jun 12, 2011)

Thanks for the clarification. I checked the website of Hammerlite (at masterchem.com). It seems like a serious product. I'll try and find it.

Ironically, the FAQ's on the website state "DO NOT use any rust converter, or any other acid or conversion type product to clean or prepare a rusted surface before applying a Hammerite coating."

Seems like rust converter isn't very popular with anyone


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## acmasterpainter (May 15, 2011)

maybe things are different in US, but where I come from hammerite is a DIY dunce product, and doesnt do what it says on tin. there have to be better than that


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## Retired From Paint (Jun 12, 2011)

Stay away from Hammerite.

One of the manufactures I worked for made Hammerite (Tacoma WA.)
our customer service department hated the stuff they were on the phones
all day long with problems #1 complaint recoat time and cure time.
The product was very durable not all bad.
The service department was very happy when it was sold to Masterchem.
Your contractor can thank me later.

As for the Iron-- The choice to use a converter was not a bad one I would
question using 3 coats of it. To much acid is not good, but can be washed off prior to your topcoat.
Finish it off with a good quailty Industrial enamel or equipment enamel this should give you a good service life without breaking the bank.

Best Reguards


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## Einhorn (Jun 12, 2011)

It turns out that Hammerite, for good or for bad, is not an option since its not sold in Canada. Contacted the manufacturer today and they confirmed this.

Started looking into Rustoleum Industrial Enamels. This IS available in Canada, with effort. I notice that it comes in a few standard colors..."black"..."gray" ...etc.. I'm assuming that its unlike standard paints where you can colour match. What I need is a very dark black, so perhaps I can achieve this by mixing the grey and black?

Would this "industrial" product really be significantly better than your standard oil-based enamel that I might find more easily from Benjamin Moore or another well known paint manufacturer?

I guess what I'm looking for now is two or three names of solvent-based / oil-based enamels that should give good results. I appreciate that the Hammerite is one, but its not available. The Rustoleum is "supposedly" available via special order from one industrial supply store, and the second industrial supply store shows it on their website but when you click it shows its been replaced by a lower VOC (v7400) product, significantly more expensive.

Thanks again for any advice on which enamels I can buy that should give good results.


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## hammerheart14 (May 29, 2010)

Well, then find a good oil based industrial enamel from a Ben Moore, Sherwin Williams, PPG, Pratt & Lambert, paint store. They should still have oil up in Canada I think, in either semi gloss or gloss.


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## Einhorn (Jun 12, 2011)

As a side note, I spoke to the local rep for PPG today. His thoughts:

-Although VOC rules are not in place yet in Canada and you can still buy high VOC paints, its such a small part of the market that he doesn't even know what to recommend.

-He feels that oil based enamels of your hardware-store variety had improved over the years so they're probably almost as good as the "industrial enamel"

-His recommendation for the "ultimate" product was 2 coats of their epoxy paint (Amerluck) followed by 1 coat of their polyurethane paint (Amershield), which prevents the chalking of the epoxy paint. But he also went on to add that unless the paint contractor was experienced with such a multi-paint type job, not to even consider it. He also pointed out the expense of this compared to oil based enamels.


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## hammerheart14 (May 29, 2010)

All you gotta do is find a reputable, well know local paint store, ask for a guy with some experience, and ask him if they carry a good quality oil based industrial finish. Chances are any good paint store will.


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## mustangmike3789 (Jun 11, 2011)

i agree with pacific. rust converter changes the color o rust but where is the protective value after that. cathodic and anodic protection is a proven way to prevent corrosion. removing a link (moisture) from a corrosion cell will stop rust. since all coatings are permiable and will allow moisture to migrate, rust blooms will eventially reoccur and damage the coating. zinc is a great product for cathodic protection but in my experience, it is not user friendly when applied with a brush for spot priming. the metal should be cleaned to at least near white metal and 1-3 mil profile. i feel that another good option over zinc would be an aluminum epoxy mastic. this can be applied over most existing coatings and over tightly adhered rust that has been wire brushed and solvent cleaned.


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## Einhorn (Jun 12, 2011)

*Head-to-Head Comparison?*

Please indulge me in this: at this point I'm tempted to conduct an experiment comparing some of the options suggested. You can not see two railings from the same spot so any differences in appearances would not show. A neighbouring building is interested in taking 1/2 the rust converter we purchased, in bulk off our hands. So IF I was to conduct such an experiment:

1.) One section of railings would be done using the method described by Pacificpainter
a.) remove all rust-sand to bare metal
b.) apply Zinc for cathodic protection (can you recommend a few names of products)
c.) Anodic passaviation - 100% acrylic exterior membrane paint (can you recommend a few names of products?

2.) The method recommended by the PPG rep (with the caveat that it had to be done right)
a.) Remove loose rust then apply 2 coats of rust converter
b.) apply 2 coats of their epoxy paint (Amerlock)
c.) apply 1 coat of their polyurethane paint (Amershield). (PPG also makes Pithane which is Urethane based...I'll check why he didn't mention that)

3.) Benjamin Moore Alkyd Enamel KP22 (Industrial product with Titanium Dioxide, 394 g/L VOC) (an alternative is Rustoleum)
a.) Remove loose rust then apply 2 coats of rust converter 
b.) paint with BM Industrial Enamel KP22. The painter recommends 1.5 coats of enamel...1 coat, then touch ups.

4.) Benjamin Moore Exterior Alkyd Enamel 133 (although the name says exterior, the spec sheet describes it as Interior/Exterior...so presumably it’s not a high VOC content, but that’s not listed on the spec sheet.
a.) Remove loose rust then apply 2 coats of rust converter 
b.) paint with BM Exterior Alkyd Enamel. The painter recommends 1.5 coats of enamel...1 coat, then touch ups.

5.) Local brand of Exterior Oil Based Enamel. Our painter points out that Benjamin Moore is always more expensive than local brands ($70/gallon for BM vs. $50/gallon for a Canadian brand (Sico). He feels that the added expense isn't justified given that we're already using multiple coats of rust converter. Since he's being paid for labor separate than for paint, his motivation for recommending the less expensive paint would not be to maximize how much he takes home from the job. 
a.) Remove loose rust then apply 2 coats of rust converter 
b.) paint with the oil-based enamel. The painter recommends 1.5 coats of enamel...1 coat, then touch ups.


So, assuming that I've got the time on my hands to arrange this, I'm really interested to put these head-to-head, any suggestions? Any of the 5 options that I should simply remove or alter? 

For example the PPG epoxy followed by Urethane method 'sounds' fantastic...their literature shows it being used to paint nuclear reactors, the hoover dam bridge, possibly some Nasa use too. Or is this just marketing?

The cathodic-Zinc/anodic/acrylic method sounds excellent, but I don't have any names of products to buy.

And of course, of the 3 Oil-based enamel methods, I'd like to narrow it down to one. 

I know such a comparison seems overly ambitions or unnecessary to many of you. But I've heard such diverse opinions in this forum, from paint companies, and from the paint contractor. So if I'm willing to try this, I hope you can guide me in which products, exactly, to purchase for each method.

In exchange, I'll gladly document the results and report back over the next few years.


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## mustangmike3789 (Jun 11, 2011)

http://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/zinc.cfm


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## hayman (Jun 16, 2011)

For industrail enamel type paint try a Shwerwin- Wilaims store near you preferably one that handles their industrail paint as they would have more experience proabably. I found the store in my area were very knowledgable. Also if you have say a Greggs Distributors in your area they carry an industrial enamel paint for $160/5gal. See attach. May be an option for you but not sure if it fits your needs.


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## Einhorn (Jun 12, 2011)

Painter started yesterday, on one balcony which I supervised. Affter grinding off any loose rust and paint, he put the rust converter in his spray gun and began spraying. 

The amount of rust converter that was required to coat everywhere was surprisingly high. Since we're talking about railings, its not surprising that a lot more is required when spraying than when using a brush. But at this rate, we would use $4000 of rust converter.

He says that he prefers spraying because it gives an even coat everywhere. So he will simply turn down the rate at which it sprays the converter in order to cover everywhere with what we have.

Only about 10% of the railing is rusty, and that's been ground down. The rest is the original paint, which has been left on since there's no sign of rust. Spraying that 90% with rust converter does give everywhere a smooth coat. It does etch the old paint which the documentation says will serve to prime the old paint. 

But I'm thinking that a better strategy would be to only put rust converter on areas where there's rust, and/or rust that's been ground to metal. We would get more rust converter on these spots, the spots that turn black, but at the expense of using it as an expensive 'etch/primer' for the old paint. The old paint could be painted over in a standard way (either just straight paint, or if needed a standard primer then enamel paint). 

Which of the two options above would you recommend...thin layer of rust converter everywhere, or save it and focus it on the rusted areas?


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## Einhorn (Jun 12, 2011)

*DOT Studies on Aluminum Mastics*

I was just about to go out and get an Aluminum mastic. If Zinc is the best, Aluminum sounded next in line, and ideal if you weren't planning on sanding to bare metal. But then I did a bit of reading. To my surprise I came across an extensive NJ DOT study comparing all coatings across mutliple NJ bridges over multiple years. The compare both organic and inorganic zinc, aluminium mastics, rust converters, alkyd based paints, epoxy paints, urethane, even galvanization. The major conclusion is: " Of the liquid-applied coating systems, those containing an inorganic zinc or organic zinc primer performed best. *The epoxy systems and aluminum-mastic** systems performed worst. *"

Here are links to the full text of the article without diagrams:

http://www.metalize.net/index.php?option=com_content&view=article&id=73&Itemid=93

and here is the link to a pdf of a presentation with lots of photos and graphs:

http://www.nesmea.uconn.edu/pdf/nesmea08_Farschon%20400.pdf.pdf


Similarly the federal DOT did a study and concluded “Recent and ongoing FHWA-sponsored test programs have found that epoxy mastic type coatings have performed relatively poorly as a generic class”:
http://www.fhwa.dot.gov/publications/research/infrastructure/structures/bridge/mastic.cfm


I guess, like everything else, your mileage may vary, but these articles, in particular the NJ DOT one, seems quite comprehensive.


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## TJ Paint (Jun 18, 2009)

Einhorn said:


> Painter started yesterday, on one balcony which I supervised.
> 
> Which of the two options above would you recommend...


I'd get pissed if you were watching me work.


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## straight_lines (Oct 17, 2007)

hammerheart14 said:


> Well, to clarify, the oil based rust destroyer was bar none, the best metal primer I have ever sold, used, ect. SO, if you COULD GET THAT, then yes, use an oil based industrial enamel to go on top. BUT if you can't get te hoil based rust destroyer, then you have no choice but to go with the water based products. AS FAR AS THE FINISHES GO, I TRULY BELIEVE that the newer water based industrial enamels are just as good as the old oils, but i DO believe that the oil based rust destroyer (metal primer) was and is untouchable. Did I clarify myself?


I whole heatedly agree. Rust Destroyer is the very best rusty metal primer I have used to date. If it can hold of on the NC beaches on the Atlantic Ocean then you can bet most any other application it would be fine.


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