Epoxy primer

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[[Image:54_Dodge_Coronet_in_primer.jpg|right|thumb|350px|A 1954 Dodge Coronet body with a fresh coat of epoxy primer.]]
 
[[Image:54_Dodge_Coronet_in_primer.jpg|right|thumb|350px|A 1954 Dodge Coronet body with a fresh coat of epoxy primer.]]
  
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Epoxy primer/sealer is a non-porous finish that is typically recommended as the first basecoat over bare steel. Epoxy primers are also used as tie coats to other materials such as composites, plastics etc. Each product is formulated differently so its important to check with the manufactuers's data sheet to check the exact surface preparation procedures for the various substrates.
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==Overview==
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Epoxy primer/sealer is a non-porous finish that is typically recommended as the first basecoat over bare steel. Various epoxy primers can also be applied over [[Fiberglassing|fiberglass]], plastic, or the black iron phosphate coating that remains after "converting" [[rust]]. Care must be taken to observe the epoxy maker's recommendations in preparing the surface over which the epoxy is applied.  
  
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New formulations of epoxies are now being marketted by most manufacturers as surfacing primers. Those epoxy hybrids are direct to metal surfacers that act as both an epoxy and a 2k surfacing primer. The convenience of those formulations lie in the fact that you only need one product where two were previously needed.
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Real epoxy primer is a two-part mix, with a hardener that has to be added before spraying. The common epoxy paint you buy at the local hardware store in an aerosol can is not considered a true epoxy primer.
  
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One word of caution with any epoxy formulation. Epoxy resins don't like acidic environments, some paint will not harden when an acid is used on the metal first. There is no need to treat metal with metal treatment prior to epoxy priming. Actually, some manufacturers specifically forbid the use of metal treatment before the application of the epoxy primer. Primer simply does not adhere to the metal when acid is present...One epoxy that is common in the hotrodding community is House of Kolor KP2-CF. That primer and any other epoxy formulation from Valspar must not be sprayed on metal that was treated with metal treatment (Ospho, Picklex etc...) or it will delaminate...  
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==Body filler and epoxy primer==
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Body filler and high-build primers can be used on top of epoxy primer. Although body filler is commonly applied to bare metal, applying epoxy primer before the filler adds adhesion, corrosion protection, and durability. Body filler is thought to be best applied over epoxy primer within the primer's recoat window time.
  
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Epoxy primer is a two-part mix, with a hardener that has to be added before spraying.
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Epoxy is porous while curing. The body fillers are designed to attach to a rough surface and can put their strands into the porous surface of the epoxy. As the body filler heats up while it cures, it causes the epoxy under it to cure faster too. As the epoxy cures, the holes close up around the strands of the body filler, creating a stronger bond.
  
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Commercial body shops may not use epoxy primer under body filler because it's not time-efficient. An extra day must be allowed in the repair process for the epoxy to begin curing before filler can be applied. However, some car manufacturers specifically require epoxy primer to be used under body filler for certain applications.
  
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==Body filler and epoxy primer==
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==Spray (rattle) can epoxy primer==
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There is a debate amongst proffessional bodymen with regards to using body fillers over or under epoxy primers. Many advocate that it is best to use body filler directly onto metal as it provides better adhesion. Others refer to the corosion protection advantages of the epoxy before body filler method. However, no one is quite sure how to deal with the sand through around a body filler that is put onto epoxy. The epoxy layer is compromized around the island of body filler...what to do then before adding another coat of body filler? Trying to keep a layer of epoxy primer under a body filler repair is just not practical sometimes. Its much simpler to add body filler direct to metal and it works just fine.
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Because epoxy primer must be mixed prior to spraying, it hasn't conventionally been available in a spray can. However, aerosol 2-component epoxy primers have recently been introduced, and are available from [http://www.rustoleumibg.com/product.asp?lvl=P&pnv=2&snv=1&pid=281 Rust-oleum] and [http://www.rubber-seal.com/prodview.asp?prodID=2068 Rubber-Seal]. To release the activator into the primer, a plunger is inserted into a stem on the bottom of the spray can. A review of one such product is available in [http://www.hotrodders.com/forum/solvent-resistant-real-2k-epoxy-aerosol-can-143345.html this discussion].
  
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One word of caution though with filling with body filler over a welded seam or any seam that could let any humidity through from the back side of the repair (all welds could be porous, have pinholes through to the other side of the weld although the are not readily visible). It is good practice to use a water proof body filler in those cases or use a good coat of epoxy on the weld seams to prevent any humidity from reaching the body filler from the back side. Regular body filler is not water resistant and the talk in them will swell if exposed to humidity. Waterproof fillers that can be used are milled glass and all metal types which will not swell as readily when exposed to humidity.
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==Cautions==
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Epoxy primer manufacturers may have very specific recommendations as to how the surface must be prepared, especially in regard to bare metal. Many topcoat failures can be traced all the way back to improper metal preparation, so it is critical to follow the manufacturer's advice regarding surface prep, and to be fully familiarized with proper procedure regarding any prep chemicals to be used, especially acids of any kind.
  
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Note that commercial body shops don't generally use epoxy primer under body filler because it's not cost-effective. However, a very limited number of car manufacturers specifically require epoxy primer to be used under body filler for certain specific applications for guarantee conformance.
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===Temperature===
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The temperature of the air and of the metal '''must''' be taken into account -- it must be high enough for the epoxy primer to properly cure. Note that in cold weather conditions, surface temperatures can be far lower than air temperatures. If the surface temperature drops below a particular value specified by the product manufacturer (usually around 60 degrees F) before it is fully cured, the epoxy may not properly cure even with later applications of heat. A non-contact thermometer can accurately determine if the surface to be sprayed is being maintained at an acceptable temperature.
  
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==Spray (rattle) can epoxy primer==
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===Acids===
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Because epoxy primer must be mixed prior to spraying, it hasn't conventionally been available in a spray can. However, "aerosol 2-component epoxy primer" has recently been introduced by [http://www.rubber-seal.com Rubber-Seal]. To release the activator into the primer, a plunger is inserted into a stem on the bottom of the spray can. Product literature states a pot life of four days.
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Some epoxies do not cure properly if put over an acid surface. If you use an acid you must be sure all the acid is neutralized before you paint. Acid residue may prevent the epoxy from properly curing.
  
 
==Tech sheets of epoxy primers recommended for automotive use==
 
==Tech sheets of epoxy primers recommended for automotive use==
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===Akzo Nobel===
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*[http://www.globalsafetynet.com/akzonobel/pdfs/akzo_195_english.pdf SIKKENS Autosurfacer EP (Epoxy Primer) ]
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*[http://www.globalsafetynet.com/akzonobel/pdfs/akzo_156_english.pdf LESONAL Epoxy Primer Sealer]
  
 
===DuPont===
 
===DuPont===
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===Southern Polyurethanes===
 
===Southern Polyurethanes===
 
*[http://southernpolyurethanes.com/Tech%20Sheets/Epoxy%20Primer.htm Southern Polyurethanes Epoxy Primer]
 
*[http://southernpolyurethanes.com/Tech%20Sheets/Epoxy%20Primer.htm Southern Polyurethanes Epoxy Primer]
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===Transtar===
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*[http://www.tat-co.com/product-files/data-sheets/data-sheet-2k-epoxy-primer-sealer-6131-english-2.pdf 2K Epoxy Primer/Sealer]
  
 
===Valspar===
 
===Valspar===
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[[Category:Body and exterior]]
 
[[Category:Body and exterior]]
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[[Category:Good articles]]

Latest revision as of 23:24, 30 May 2023

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