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"To Prime or Not To Prime"

The PRIMER Primer Page

(epoxy primer, epoxy sealer, epoxy waterproof)

Progressive Epoxy Polymers, Inc.

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

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

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Most of this page is useful background information on primers. Toward the bottom of this page is a special section about Primers and Floor Epoxies for applications on cement surfaces - CLICK HERE.

DISCLAIMER: Progressive Epoxy Polymers, Inc. are sellers of epoxy coating , resins and other coating products. The suggestions - procedures outlined above are given AS-IS without any warranty and in no way expand the rights under which you have, or will purchase, this product or related products. Your use of any of these suggestions/procedures is at your sole cost and risk. You must make an independent determination whether to follow any or all of the above items based upon the numerous application variables at hand.

There seems to be two completely different worlds when it comes to primers, the 'consumer' world and the 'industrial' world. In the consumer marketplace primers are either oil based or waterbased. That's it. The real world of primers in much more complex and if you're really interested in coatings you need to skip the nearly useless world of consumer primers and become knowledgeable 'industrial' primers.

SPECIAL NOTE: solvent free epoxies (0% VOC) are generally considered to be self priming, (no primers needed). However, without solvents, there bond is strictly a surface event so dust, weathering, very dry surfaces (such as repaint putties) etc. can provide a less than perfect surface for them to bond with. A solvent based epoxy primer, with the solvents penetrating the surface a little bit, can provide a better, well bonded, fresh, epoxy surface for a solvent free epoxy to adhere to.

NOTE: --- Professional painters and other experts seem to ALWAYS use a primer on everything they do. More and more, I am tending to see the value in this approach.........

PRIMERS: The definition of a primer is rather general. It is generally considered to be a coating that improves the adhesion or perhaps more important, the performance, of the topcoat coating. For water or solvent based coatings, such as enamels, 1 or 2 part urethenes, or latex paints, require water or solvent to evaporate away in order for the coating to cure. On porous surfaces, such as wood, wallboard, cement, etc. the water or solvent may soak into the surface and not evaporate when, where, or how it should for the coating to achieve it designed properties. A primer coat is used to 'seal' the surface so that the solvents or water will be able to evaporate away as they were designed to.

Secondly, primers DO soak into porous surfaces and thus provide a really strong bond between the primer and the substrate, with the primer then providing a clean, fresh non porous surface for the top coating to adhere to. This is called a Tie Coat. This is also important over weather damaged fiberglass or dusty, crumbling concrete.

Tie coats can also provide a a sticky bonding coat used when a very ‘dry' coating is applied to a dry surface. For example, a very dry putty or filler - patching compound being applied to wood, fiberglass, metal, or concrete. Here we have ‘dry on dry' and the ability of a very dry putty to stick to a dry surface is limited. A tie coat could be a wet, sticky, or still tacky coating of ‘regular' epoxy applied to the surface with the putty or filler applied upon the still tacky epoxy tie coat.

Many commercial primers also have anti-corrosion additives in them for use on metalic surfaces.

.. CLICK HERE TO GOOGLE SEARCH OUR ENTIRE WEB SITE FOR KEY TERMS/WORDS ..

More on woodsealing/waterproofing - www.epoxyproducts.com/woodseal.html

More on primers - www.epoxyproducts.com/primer.html

PRODUCTS: ESP 155™ - marine catalog ------ home catalog

Water Prime™ - marine catalog ----- home catalog

Aluthane™ (moisture cured urethane) - marine catalog ----- home catalog

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Always seal/waterproof with TWO coats of any product.

Solvent based products best on smooth surfaces, in cool temps, and high humidity.

Epoxes are one of the best undercoats/primers

NOTE: these products not avail. in all parts of the country (VOC restrictions)

MSDS & Data Sheets (buy only from vendors who make these available)

TYPES OF INDUSTRIAL PRIMERS (QUICK/SHORT LIST)

* Epoxies (with or without solvents added for improved penetration). Epoxies have outstanding bonding to most surfaces and they form a non-porous surface. Epoxy coating are thus often considered self priming (although sovlents are sometimes added to solvent free epoxies to improve penetration on porous surfaces, usually as a 'first coat' followed by a second coat of epoxy without the addition of any solvent).

* Moisture cured urethanes. Used by contractors in areas that cannot have 'by the book surface preparation, because they have great bonding and lots of solvent to 'soak' into surfaces. our Aluminum filled moisture cured urethane, Aluthane, is an amazing product. It technically is not just a primer, but an excellent coating all by itself. Latex tends to not like the smooth finish but enamels go over it fine. It forms a hard surface so that sanding is recommended if it is not topcoated within 24 hours.

* Phenalic based primers. Phenalic sort of means plastic. It is a solvent based (oil based in consumer lingo) but instead of just some sort of diluted enamel like paint, these one part primers contain phenalic resins and usually anti corrosive additives. They are the universal primers in the commercial world (but probably not as good a primer as the epoxy or our Aluthane mosture cured urethane, but more user friendly and it accepts latex topcoats better).

Below are listed some application surfaces with comments about each regarding coating them with a solvent free epoxy.

METAL SURFACES: Usually metal surfaces (except maybe aluminum) are simply sandblasted etc. and the coated with epoxy paint, in other words, no primer. But, options include:

1) a Moisture Cured Urethane (MCU) is often used as a primer. We offer an aluminum filled MCU (Aluthane) as both a primer (for lots of surfaces) as well as an attractive topcoat

2) MIO (micaceous iron oxide) - a common (in Europe) paint or epoxy additive

3) zinc based primers (we don't carry any of these) - provides 'electrical' protection (vs. a mechanical barrier of regular epoxy)

4) salt removers - (we don't carry them) removes unseen, damaging salt ions on the metalic surface

FIBERGLASS SURFACES: Mixed reviews here. New fiberglass does not need priming (according to many sources). However, there are many cases where I personally think it would benefit by improving the bonding. One is on old and/or weathered fiberglass. Time, water, chemicals, and sunlight certainly negatively affect and weaken the fiberglass surface. Priming consolidates that weakened surface. Secondly, I suspect that dust and dirt from sanding gets ground into the hull and doesn't completely get removed with a hose and/or solvent wipe-down. This sanding dust is not what you want your epoxy to bond with. Primers probably soak in and around these dust particles, mitigating their negative impact. I don't think I would use a primer over a painted fiberglass surface or a sanded one that still has a lot of the old paint remaining upon it. The solvents could weaken or react with the old paint (but probably not). However, they will not 'soak' into a painted surface well enough to provide an 'enhanced' bonding surface. Options:

1) solvent thinned epoxy - add solvent to your favorite solvent free epoxy or purchase one already solvent thinned (like our ESP 155)

2) a Moisture Cured Urethane (MCU) is often used as a primer. We offer an aluminum filled MCU (Aluthane) as both a primer (for lots of surfaces) as well as an attractive topcoat

CEMENT/GUNITE SURFACES: Mostly floors/slabs, swimming pools and commercial structures. Concrete is a porous surface. In worst cases the cement is weak and crumbling (pool chemical damaged gunite is a good example). Coatings will bond to it, but then peel off usually taking the top layer of sand grains with it. Solvent thinned epoxy or similar primers, will 'soak' into the cement, firming up the weaken surface of the cement.

Moisture in and traveling through the concrete can also cause coating failure. Primers are not just used on old, weathered, or 'sandy' cement to improve the bonding, but also to reduce 'outgassing' which is the air inside the cement that is sometimes released (such as when the temperature is rising). The released air can form bubbles and craters in the hardening epoxy. On cement garage floors, some contractors always put down a primer layer (either a waterbased floor epoxy or a solvent thinned epoxy coat), but many do not. It is possible (I don't really know) that a primer coat will help 'seal up' problem areas that have been degreased (note degreased areas sometimes seem to still have adhesion problems).

Our water based Water Bond is a good primer option (found at ww.epoxyproducts.com/b_floor.html). Some professional applicators use water based primers, some use solvent based primers. A second option is our solvent thinned ESP 155 epoxy or adding your own solvent to our Low V clear epoxy. Finally, you can add solvent to the first coat of our Industrial floor epoxy (say 10 to 15% solvent). The primer coat should be applied thin. If using the Low V epoxy thin with about 24 oz of solvent (xylene) per 1.5 gallon unit of the Low V epoxy. Low V epoxy is found in the www.epoxyproducts.com/d_clear.html of our catalog.

Recent industry trade magazIne articles seem to suggest that on concrete a water based epoxy primer might be best because if its possible ability to 'bind' water/mineral solutions and soluable mineral salts found in the concrete. These minerals can cause problems in the future by attracting moisture and causing 'ionic' concentrated 'cells'.

Options:

1) solvent or water based epoxies (solvents help the epoxy to 'soak' into the cement, firming up the weak surface). They also help seal the concrete reducing outgassing bubbles in the epoxy topcoat.

2) our Bio Vee Seal is not really a primer, but a product that reduces the 'bad news' moisture migration through the cement that can cause bond failure (and musty smelling basements)

WOOD SURFACES: Primers are suggested for wood because wood expands and contracts with moisture, while surface coatings expand and contract with temperature. Keeping the coating and the wood together requires a very good bond and 'penetrating' primers help achieve that. Also, the wood may contain a lot of moisture and/or rot (i.e. old window sills, etc.), Primers will provide a dry, sold surface for the epoxy or non-epoxy topcoat to stick to. Presonally I have found that the Aluthane bonded to old RR ties and a porch deck when nothing would. For plywood (to reduce checking and seal the edges) I would use a solvent thinned epoxy.

PRIMER TYPES

SOLVENT FREE EPOXIES - not really a primer, but other coatings do bond well to solvent free or low solvent epoxy coatings. For marine, boating, and commercial projects such as floors, epoxies are a common coating.

PENETRATING EPOXIES AND EPOXIES WITH SOLVENTS ADDED (GENERALLY THE SAME THING): Again, technically not a primer but rather a waterproofing coating. Despite what is written in the above it is not uncommon to find end users of modern solvent free epoxies to add some solvent (MEK, Acetone, xylene, etc.) into their epoxy coatings, especially on the first coat of a multi coat system. It is assumed that the solvents help the epoxy ‘soak' into the surface better, producing a better mechanical bond. The solvents also do other things: they thin the epoxy; they extend potlife, increase coverage (because the epoxy is thinner); let the epoxy flow off the brush or roller better (nicer). They also then to reduce the epoxies physical properties, especially hardness. It the "wood industries" such as boatbuilding/repair and building restoration solvent thinned epoxies are often labeled "penetrating epoxies" and may contain up to 70% solvent. Such penetrating epoxies can either be purchased or home grown by adding solvent to a thin marine type epoxy. (note: Progressive Epoxy Polymers offers two of these, CM 15™ high build, low solvent epoxy mastic and/or topcoat, -- ESP 155™ (cannot be sold in Southern California) low solvent penetrating, cycloaliphatic, clear epoxy waterproofer).

Some epoxies can react with alkyd (oil enamels) under certain conditions. (see www.epoxyproducts.com/enamel.html). The preventative / fix is a coat of aluthane. Aluthane is covered in the MCU section below.

Use ESP 155 to 'seal/prime/smooth'

patched and repaired surfaces.

ZINC PRIMERS: Zinc primers generally fall into two types, organic or inorganic. Inorganic zinc primers are often something like a layer of zinc plated to the surface while organic zincs are more typically represented by zinc dust in some sort of paint (epoxy, urethane, etc.). Inorganic zinc primers have been used for many years below the waterline on ships. There is still some uncertainty about using organic zinc primers below the waterline, although that is probably based more upon the coating it is combined with rather than anything related to the zinc itself. Inorganic zinc primers are probably more durable and perhaps more effective, but organic zinc primers may be easier to apply.

Zinc primers are corrosion fighters and are used on steel surfaces, often under epoxy. While epoxies prevent corrosion by forming a barrier surface stopping moisture and oxygen from reaching the steel, zinc layers resist corrosion chemically/electronically. Thus, a zinc primer under an epoxy topcoat creates a system that fights corrosion by two different mechanisms. We do not offer a zinc primer.

MIO BASED COATINGS: For over a hundred years paints containing MIO (micaceous iron oxide) have been used to fight corrosion. They are more common in Europe than in the USA. The Eiffel Tower in Paris is often cited as poster child for MIO based coatings. Like inorganic zinc, MIO can be added to several different coating products. It is basically a plate like iron based pigment. These plates stack up on top of each other forming an extremely tough, non porous, protective boundary that improve the barrier affect of the coating. As you might expect, most MIO primers have that ‘dark red/rust' color. We do not offer a MIO primer, but we do offer MIO powder additive (in our fillers/mix in section).

MCU: Moisture cured urethanes (MCU) are one part urethanes that cure by taking moisture from the air. These solvent based coatings have a tremendous bond and are often used by contractors as a primer on surfaces that have not received ‘ideal' surface preparation. MCU coatings are available with zinc, aluminum, and MIO pigment providing the primer types mentioned above. I have personal experience with an MCU that used aluminum flake pigment that appears to work sort of like a hybrid between the zinc and MIO systems. It is classified as a metalic coating. This aluminum MCU (Aluthane) is an amazing product (which we sell) that can be used as a primer or topcoat with an attractive ‘galvanized' look and amazing adhesion. It makes old boat trailers look showroom new. Note: latex paints don't go over aluthane nicely (like latex over oil based paints). Sovlent based coatings (urethanes, enamels etc.) do cover aluthane nicely. Some epoxies can react with alkyd (oil enamels) under certain conditions. (see www.epoxyproducts.com/enamel.html). The preventative / fix is a coat of aluthane.

More about our Aluthane product (5/05): from personal experience I can say that it makes a great primer, bonding solidly to surfaces that other coatings will not. I personally like it on wood (really soaks in!) such as porches etc. It can be painted over with latex or enamel without problem (or left alone). What's really nice is that when sanded lightly it gets darker in color, so when used as a primer/sealer, a bit of sanding will show high (dark) spots and low (lighter) spots as you sand smooth the surface. It goes on quickly and easily and no mixing! The chemists behind Aluthane recommend sanding it if not topcoated within about 16 hours (this is a 'bummer' for a primer).

SOLVENT BASED ( 'OIL BASED' -- but "phenalic" - better than 'homeowner 'oil based) PRIMERS: phenalic based primers - better than the 'consumer oil based' primers, availability unknown.

INTERNAL CONCRETE SEALERS: Concrete slabs located on the surface or below grade can be extremely difficult to permanently coat, especially if they do not have a vapor barrier. Moisture and soluble mineral salts can travel through the porous concrete and wreck havoc with coatings. Existing moisture in the concrete, and perhaps any moisture migrating through the concrete can cause bonding failure or weakening, Worse yet, dissolved mineral salts will reform the crystal structure when the moisture is removed (evaporated etc.) and these growing crystals can exert 1500 pounds or more of pressure as they grow. Few coating systems can resist this kind of prying pressure.

There is a class of concrete sealers that reduce the porosity and permeability of concrete by sealing them internally, rather than by some sort of surface film or coating. These water based coatings literally soak into the concrete and as the water evaporates, forms tiny crystals inside the pore spaces of the concrete. The method is that of ‘clogging' up the concrete with the associated reduction of both porosity and permeability. It is the concrete equivalent of Gor Tex (tm) - a breathable, but water proof surface. We offer such a product called Bio Vee Seal.

SOLUBLE (INSOLUBLE) SALT REMOVERS: Cutting edge research shows that salt ions form a special, hard to remove attachment to steel surfaces even after they have been sand (abrasive) blasted clean or even water jetted down to bare metal. These ions are hydrophilic and attract moisture which creates a tiny electric cell that forms a corrosion site and leads to premature coating failure. Special wash products are available that remove these invisible ‘soluble' salts. The problem can also be present on concrete, fiberglass and other surfaces. Visit our site at: www.epoxyproducts.com/salt.html for more information. WE DO NOT SELL A SALT REMOVER PRODUCT AT THIS TIME.

WATER-BASED EPOXIES: Water based floor epoxy systems for concrete surfaces are becoming more common and are now sold in the ‘Big Box' hardware superstores. Being water based they tend to ‘soak into' the concrete surface to some degree, thus resulting in an outstanding mechanical bond and few coating failures for ‘Do It Yourselfer' coating their garages and basements. While these coatings are ‘stand alone' for light traffic situations, commercial users are beginning to see these ‘thin' water based floor coatings as ideal primers under more traditional, often solvent free, industrial grade floor epoxies. Our med gray water based floor epoxy is called Water Bond.

Knowledge is Power - We like informed consumers!

Learn the basics of epoxy at our educational EPOXY 101 page - Click Here .

Finally, email us back with your questions or comments before you buy - EMAIL HERE

Progressive Epoxy Polymers, Inc.

Most of this page is useful background information on primers. Toward the bottom of this page is a special section about Primers and Floor Epoxies for applications on cement surfaces - CLICK HERE.

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