Surface Preperation For High Adhesion?

Abrade the surface of the steel first?

Abrade the surface to allow some tooth for the epoxy to adhere to. Also, everything must be clean, clean, clean. It sounds like a contamination issue could be the root cause.

You should clean the surface with a solvent such as acetone first. Then follow that with a neutralizer solution. I am not sure what makes the best neutralizer, but you might check omega.com and look at surface preparation for steel when applying strain gauges. They sell a strain gauge bonding kit that contains a bunch of cleaning chemicals. Even if you are not attaching strain gauges I think the knowledge they have is applicable to your needs.

I have had success applying strain gages in this way. There is a technique to cleaning the steel. You must wipe the surface with a "clean" or sterile wipe and always wipe in the same direction. Discard the wipe with each pass. I use sterile cotton balls, but they leave fiber residue, so a gauze type of wipe might be better. Never touch the steel surface once cleaned. Oils from your hand will contaminate the surface again.

Finally, you must take into consideration what operational and storage temperature the part will live in and the environmental conditions as well (i.e., humidity, salt, etc.).

I use a heat cured epoxy for my strain gauges. I cook it at 100-150° C for a few hours and then you can apply a post cure heat soak if your application requires.

Never touch the steel surface once cleaned. Oils from your hand will contaminate the surface again.

It is also very important to guarantee that the prepared surface is completely dry (and maintained bone-dry) and oxide free. Steel surfaces will oxidize extremely quickly (at the molecular level) and can reduce adhesion.

sorry this message for try.

Sand or grit blast & burn out [heat in an oven] as if you were powder coating.

The common error is not cleaning the surface prior to sandblast or sanding the surface to be painted. SSPC-SP1 is a standard procedure to clean steel: it show you exactely how to clean your surfaces.

I recommend the use of a biodgradable waterbase surface cleaner instead of solvent wipe. This keep you away form waste solvent, special container for used rags, fire or explosion hazard, extra money for waste solvent disposal, boom room and best thing it may lower you insurance fees!

Here's some few questions you should ask:

Epoxy paint usually have very good adhesion on steel and are mostly surface tolerant: did you check with your supplier if you got a possible bad batch of paint?

Was your steel correctly cleaned? Any possible contamination occurs after the cleaning and prior to sandbast or sanding?

Did you use the correct amount and the recommend thinner? The use of recycle thinner (or lacquer thinner) may affect the coating drying time, adhesion etc...

For sandblast ask or do an angular profile it will give you a better mechanical adhesion. What kind of profile do you got once parts are sandblast?

The type of sandblast: are you asking or doing a commercial blast SSPC-SP6 (Nace#3) or an SSPC-SP10 (Nace#2). Use SSPC-SP3 standard as guideline if you just do a mechanical sanding.

If you are not familiar to SSPC standards I will be please to provide you a copy of these standards and recommandation for your surface preparation prior to sandblast and painting.

I use epoxy paint on the items that i fabricate. I wipe down the surface with denatured alcohol. Have had no adhesion problems.

The old adage that "surface preparation is 90% of the job" has been rewritten many times over. There are countless reasons for premature failure of coatings (of all types). One of NACE's gurus lectures that "people cause coating failures"... a discussion which, followed to the end, proves to be positively true!

NACE (National Association of Corrosion Engineers International, www.nace.org) and SSPC (formerly the Steel Structures Painting Council, now the Society for Protective Coatings) have joined forces to write Joint Standards for many aspects of surface preparation, etc. The SSPC-SP5 and NACE 1 are both (identical) Standards for a white-blast metal finish. An SSPC-SP10 equates to a NACE 2, or near-white blast finish (there are other spec-degrees as well). NEITHER of these Standards dictates the depth of the surface PROFILE (in mils; peaks-to-valleys) ... that is a parameter that needs to be separately addressed by the Coating Specification (written by either the product manufacturer or the project engineering team).

Once the Standard AND the profile measurement are known, the Surface Cleanliness Standard must be addressed. Limitations exist on the allowable chlorides, ferrous salts, nitrates, sulfates etc. that may remain on the surface prior to application of any given coating. Products like Chlor*Rid exist to help remove that specific contaminant. When (sand-or-grit) blasting is performed, pre-cleaning of the surface is required to prevent driving contaminants INTO the surface profile. During blasting, certain checks must be made to further insure against invisible surface contaminants. Blotter-tests of the compressed air, testing the blast media itself, etc...

Chemical tests are readily available to proof the surface as being ready for coating. THEN, verification of appropriate environmental conditions comes into play, as well as the mixing process, application method, verifying uniformity of the applied film thickness, and curing conditions. If you want to enjoy the full measure of performance and longevity from your coating project (phenomenal capabilities exist from todays hi-tech polymer coatings) no stone may be left unturned in checking everything of importance, or failure will find its way in!

Best of luck with your endeavors ~

If you are in a location which allows Methyl Ethyl Ketone (MEK) as a cleaner, this will remove grease and oil deposits. An abrasion with a course paper or scotch-brite from 3M and a susequent wash with MEK will give the best surface preparation other than an iron phosphate or zinc phosphate pretreatment. Use Key Polymer Key E12 A/B modified epoxy adhesive system available from Key Polymer Corp. Lawrence, MA. USA as the adhesive. All bonding should be done ASAP after cleaning to prevent contamination of the bonding surfaces. I've used a standard dishwashing detergent followed by an isopropyl alcohol wipe with good results in bonding stainless steel to aluminum with the adhesive acting as a dieletric to eliminate galvanic corrosion. Guest

One thing not mentioned so far is the importance of working the epoxy into the surfaces. There are always microscopic trapped air bubbles that cling to the crevasses, thus reducing the actual bond area AND missing some good undercuts which create the "mechanical bond" portion of the adhesive grip.

If possible, rub the adhesive vigorously into both surfaces.

Another way to improve "wetting" is to put the parts under a vacuum while curing.

"A coating is only as good as the surface it is put on" While painting a BIG drilling rig, the deck, the spuds, inside and outside and tens of wing tanks on ships and a 10 foot diameter pipe line to a length of 24 miles, I have relied on good angular quartz sand or angular steel grit g16 that will give a proper profile for the coating adhesion. Another point is the cleanliness of the abrasive, if abrasive is being reused one should see that it is not contaminated due to any previous use like using on an oily surface. The steel should be first cleaned so that it is free of any contamination, specially any oily contamination so the abrasive does not get contaminated with the oil and then sand or steel grit blasting to near white surface and then apply the coating whether it is for protection against corrosion or used as an adhesive to join something with the steel. It should be noted that you have a problem only with high carbon steel that means whatever abrasive you are using is not able to create a proper profile because of the hardness of the high carbon steel, while it works on softer low carbon steel. You could trry Silicon Carbide abrasive which is a very hard material and will easily create a good profile even at low pressures.

Abrasion is good, clean is absolutely necessary. Try a product clled Bestine, you shouldbe able to source it online.

MANY THANKS TO MY DEAR FRIENDS AND YOUR GENUINE KNOWLEDGE. I WILL TRY MY BEST TO FOLLOW YOUR ADVICES.

Abrasion iss good. You can also use bonding promoters. Try Hawk Research labs in Illinois. USA. May be the epoxy you are using too.?