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The Industrial - Commercial Grade Coal Tar Epoxy Information Page

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Paul Oman, MS, MBA - Progressive Epoxy Polymers, Inc.

Member: NACE (National Assoc. of Corrosion Engineers), SSPC (Soc. of Protective Coatings)

"Professionals helping Professionals"


In the spring/summer of 2001 I searched the Internet looking for information about coal tar epoxies. I found lots of product pages, but nothing about why and where coal tar epoxies should/could be used in place of regular epoxies. What are the Pro's and the Con's of coal tar epoxies? I have now learned these things and wish to share the information.

Please note that our company, Progressive Epoxy Polymers, Inc., recently added a coal tar to the line of epoxies and clear coat products that we sell. It is a solvent-free coal tar epoxy of very good quality (using the most modern epoxy components to a 38% coal tar base). It sells in 2 gallon kits. More information and links to our company web site are at the end of this document. So much for the advertisement/disclaimer, now the information promised above!


Background History

Coal tar epoxies are essentially a mix of coal tar and epoxy resins (and not all epoxy resins are the same). Coal tar epoxies were at their peak of popularity in the 1960's (???) through about 1990. After that, non-coal tar epoxies replaced coal tar epoxies due largely to health concerns over long term exposure and direct contact (by coating applicators) to the ‘tar'.

Advantages of Coal Tar Epoxies

Coal Tar epoxies are inexpensive compared to most non-coal tar epoxies. The offer considerably more flex (or elongation) then regular epoxies. This makes them useful on garage floors where turning/spinning tires will ‘stretch' the epoxy, as well is in situations with a lot of expansion and contraction. Coal Tar epoxies are also famous for protection from moisture, both in the water (such as barge hulls) and when buried underground (such as pipelines and underground tanks). A key advantage of coal tar epoxies is its ability to bond to oily surfaces (thanks to the hydrocarbon nature of the ‘tar').

Disadvantages of Coal Tar Epoxies

Coal Tar epoxies smell like tar/asphalt and leave an asphalt like stain on your hands, etc. when working with the un-cured epoxy. It only comes in a tar black color. Coal tar is not something you want to handle on a regular basis over a long periods of time.

Most or all of the other disadvantages of coal tar epoxies are often more about the epoxy side of the mixture rather than the coal tar side. Issues here can include solvents in the product, and poor resistance to UV (becoming more brittle and chalky), are the ones that come to mind. There are also reports that weathered coal tar is difficult to recoat or topcoat. At least some coal tar epoxies appear to leave behind an oily layer as the epoxies weather away and this layer makes topcoating - recoating difficult or impossible. The coal tar that we use does not appear to have this problem, at least it hasn't been reported to me yet.

Misc. Information

Coal tar epoxies (at least the version we sell) can be topcoated with regular paints. It can also be used with colored quartz sands or vinyl chips for decorative epoxy floors -just like non-coal tar epoxies are used.

When and Where I Would Recommend Coal Tar Epoxies

The less costly coal tar epoxy is often a better quality coating than an equally priced non-coal tar epoxy. A good quality (and more costly) non-coal tar epoxy will perform equal or better than a coal tar epoxy and will be available in colors other than black. The odor of coal tar epoxies (at least the one we sell) is not really that strong, still, I would use it in a well ventilated area or outdoors. The coal tar epoxies that I have tried (several brands) all seemed flow of the paint brush more smoothly than solvent free, non coal tar epoxies. This makes it a bit easier to apply and probably less likely to leave behind thin spots or ‘pinholes' in the coating surface.

Because coal tar epoxies will bond better than other epoxies to oily surfaces, they are more likely to remain bonded to ‘degreased' garage or work floors. I would consider their use, perhaps thinned with solvent, as a sealer/primer over such areas. The coal tar epoxy can then be topcoated with other coatings.

The much flex (bend) and elongation (pull) of coal tar epoxies (3 to 10 times the amount of regular epoxies and the only product we carry with BOTH flex and elongation - each about 25%) ) is its greatest characteristic and the case presented regarding the benefits of this property when used on garage floors, garage ramps, etc. where there is lots of rubber tire traffic, makes logical sense to me. However, I have not heard of less flexible, non coal tar epoxies failing in these situations either. Coal tar's ability to withstand moisture (old time sailors sealed their boats with tar pitch) is another important plus, but I think good quality, non coal tar epoxies offer just as good moisture sealing.

Coal tar epoxies are ‘out of style' but their usefulness has not diminished. A good quality coal tar epoxy offers a price to performance ratio that is hard to beat. Their greater flex is a real plus (although not as important in may situations as it might seem), while their messy tar staining and smell are a downside consideration. I think the decision to use coal tar epoxy can be made more on personal choice than on a point by point technical comparison, sort of like decision between an apple or orange with your lunch. Just remember that all coal tar epoxies (like all other epoxies) are not the same.

Coal Tar epoxy alternative is our black CM 15 epoxy paint - find both Coal Tar and CM 15 in our catalog - CLICK HERE

All coal tar epoxies are not the same!


Materials Performance magazine dec. 2002 - q&a section page 39

"Coal tar epoxy failure"

RE: coal tar coating failure in a sewer pump station steel wet well. After suitable surface preparation surface was coated with two coats of a polyamide coal tar epoxy. Failure of the coating was at a 5 inch zone at the top of the high liquid level. Failure consisted of softening and swelling, not blistering. The authors go on to quote from "Corrosion Prevention by Protective Coatings," a text by C.G. Munger. Munger states that CTE (coal tar epoxies) coatings are most effective in the sewage industry. However he qualifies this by stating that the amine cured CTE system is essential because of the bacterial attack on the polyamide curing agent.

The coal tar epoxy offered by Progressive Epoxy Polymers IS an AMINE cured system and not the problem causing amide system described above. Our coal tar epoxy is also solvent free (0% VOC).

CLASSIFICATION	PROFESSIONAL QUALITY "B GRADE" MAINTENANCE COATING - THIS IS A HIGH QUALITY COAL TAR EPOXY
% VOC	0% VOC, 100% SOLIDS
SHIPPING/EXPORTING	HAZMAT - ORM-D TO SHIP. CANNOT BE SHIPPED OUTSIDE THE USA OR BY AIR
VISCOSITY	BRUSHABLE, ROLLABLE
STND COLORS	BLACK
WET APPLICATION	APPLIED TO DRY SURFACES
MIX RATIO	1 TO 1 BY VOLUME
STND PACKAGING	STANDARD PACKAGING IS 2 GALLON UNIT
MISC. INFO
PRIMING

Daniel Skira -- Skira Yacht Design wrote (5/2010):

I just received my two quart of coal tar epoxy I ordered. What I really like is the literature and all the information you put with the package. It is very useful. I used normal coal tar until now, and look forward to try your product.

VENDOR COMMENTS:

Hi Daniel – Thanks for the kind words. Yes, I too like the coal tar epoxy - rolls on nicely. But coal tar epoxies have other issues (see www.epoxyproducts.com/coaltar.html - soft/flexible, may not be able to paint over especially if old and sun weathered, etc.) and I often recommend cm 15 epoxy as an alternative to the coal tar.

If you notice a difference with our coal tar epoxy it would be because of the high end epoxy part of the coal tar epoxy we use. Most coal tar epoxies have a reputation for using very low end epoxy.


Daniel Skira -- Skira Yacht Design wrote (5/2010):

Paul, – The one to one mix is absolutely the way to go. Fantastically easy. The product is very good, goes like a charm on wood, dry nicely without any shrinkage. I built the boat outside, at 50F no problem even we had light rain, no problems.

I really like your coal tar epoxy. A real time saver compared to the classic one. The quality of the coal tar is the same as the high end one component I used for almost 30 years. But yours dries! No need to wait one month anymore! No need to boil it either like the other one, to have a good penetration. Your coal tar epoxy seams to have a very good penetration. I even used on some larges holes on the keel, and it worked like a charm. Impossible to do the same with the non-epoxy one. I will be sending another order. I am hooked on yours! I will probably paint the underwater part of the hull with your coal tar epoxy. Many thanks.


Daniel Skira -- Skira Yacht Design wrote (5/2010):

Hi Paul – Just painted with regular oil based painting on top of your coal tar epoxy without any preparation. Dry neat, and seems to bond. I sanded two coats of coal tar epoxy with a belt sander and 36 grit belt, but with a light handling of the machine. Perfect, no problems. Painted on top with regular oil based paint. No problem.

So my underwater hull will be painted with your coal tar epoxy. Then I will apply a coat of antifouling. Not the sides since I know the problem of epoxy and the sunshine. The elongation of you coal tar is a perfect match for my wooden hull.
All my best. - > Daniel


Daniel Skira -- Skira Yacht Design wrote (5/2010):

Hi Paul – After curing for 7 days, the coal tar epoxy I applied to a steel bar was even not touched. I used a heavy hammer to bend the steel bar. The secret is let it cure at least 7 days and it is hard and flexible. It is the greatest coal tar epoxy I ever tried. You can post my trial on your website. This an amazing product. But I repeat, the curing time is mandatory. Sometime people think epoxy is immediate, they are wrong. I will come for more, the hull will be primed underwater with your coal tar epoxy.
All my best – Daniel

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