Why Won't Chemlok Bond to Aluminum?

Plain or anodized?

NO. First diluting the chemlok, then spraying the chemlok on the surface of aluminum tube, next dry the tube in the air for 15min, finally doing the molding with rubber. But after molding, we found that the tube surface was so clean, the chemlok just sticked on the rubber not on the tube surface, so the bondability between tube and rubber was failed....Again, thanks for your attention...

I haven't attempted bonding aluminium with rubber or cleaning with chemloc.

Pure aluminium has a tendency to "rust" quickly. The cleaning procedure with chemloc may increase the reaction.

Have you tried cleaning / preparing the aluminium with fine sandpaper?

Another idea might be to have the part anodised and thereby change the bonding characteristics .

Thanks again.

I am just the poster

Actually, the aluminum does not "rust" quickly but the steel. Also we do not have cleaning procedure with chemlok, just using the spray gun to spray the chemlok on the aluminum tube. I already cleaned the aluminium with sandpaper, but it still did not work. Faint.. As for the anodizing, it will increase cost...

Have you tried sand blasting the component in order to provide a "key" for the Chemlock to bond to?

maybe read Post #5 f i r s t

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I think that by "rust", the previous poster meant "oxidize" (which is why he put the word rust in quotes). The oxide that forms on aluminum does so very quickly (and is invisible) and can interfere with bond strength. To avoid this problem, I've used epoxy for bonding aluminum, and have wet-sanded the aluminum surface with the epoxy (instead of water), so the aluminum is shielded from the atmosphere. This seems to work well, but would be tedious in production.

I think, but don't really know, that anodizing will not help: in my experience, it hinders. Chemlok can advise.

"PS", in addition to my earlier post (probably below this); You say you are air drying.

Are you, in fact, diligently measuring and documenting the air temperature and humidity levels, Along-WITH the surface temperature of the article (tube)?

Just as with the oxide that develops before the eyes can detect it (and there are test kits to help verify the absence of oxide before starting), interference might be coming from humidity / condensation, without knowing it... unless you're in an appropriate environmentally-controlled facility. Just a thought.

Praying for your success ~

Referencing #3's comment, it's true that aluminum does quickly develop an oxide layer on it's surface (long before the human eye can see it), and this reduces the energy level on the surface.

If you haven't seen this before, read:

http://www.visionmark.com/pdfs/adhesion.pdf

One item NOT addressed within the article is the additional "grip" (mechanical-adherance) afforded by the surface roughness. Remember that sanding does not produce the same anchor profile as (proper) blasting. When preparing steel, many options of media exist, from sands to grits to various types of shot. Whereas sands produce a relatively smooth profile, grits produce a much more aggressive profile, and shot delivers a "peened" sort of profile. For aluminum, garnet tends to be the favored blasting media. Getting the right size (sieved and measured) to produce the desired profile range (peaks to valleys) is critical... as is that time-window between blast and application. You mentioned "steel" in your follow-up post. Where does IT tie-into this...?

[ There IS, most certainly, a resolve to your issue here...!]

The ref to steel is because I used the word "rust" in stead of oxidise.

I Don't get it... Why not ask Chemlok?

I have been in the engine mount business (aviation related Lord user) long enough to know that there are at least a dozen good reasons why it won't stick. and when this happen, I know where to go. Who knows better than they do? and BTW they have pretty darn good customer service...

Wangito.

You may find that roughing up with say medium grade sandpaper and then cleaning using say methylated spirits (leaves no residue) may fix your problems completely.

I suspect that the alu still has oil or grease from a previous process which is making bonding difficult.

You may have better luck by first etching the aluminum with an alkaline such as a lye solution in distilled water. this will give you a good adhesion surface without the micro-peening or silicon embedding that sand blasting or sanding can leave. It will also act as a de-greaser, but it's better to prep with a solvent de-greaser before using the etch solution.

Aluminum has a great propensity to absorb moisture; this could be part of the problem. Just for a test, hold a propane torch on the tube and see if moisture is evident. You will clearly see it as it evaporates. The xyline could be drawing out the moisture on application and creating a barrier.

Your test with a propane torch is completely untrustworthy, due to the fact that burning a gas like propane produces water vapour as part of the burning by products. These would condense out on any cold surface.

If what you say is true, you need a better test that does not in itself produce water.....electric heat might be a way......give us a revised test procedure that might work.

Cleaning with methylated spirits as I recommended, would clean off water as well as grease and other contaminants!!

First I need to say thank you to

Hendrik, zigzag,Blink,ndt-tom,wangito,Andy Germany,Zamaron,mareng

Thanks for your attention.

It is really a big problem I am meeting at present. We are building the heaters, you know, we need to end seal - bond the rubber to the aluminum tube.

1) I will look for some suggestion from Chemlok company.BUT old people said that chemlok gave two meothods: one was make sure the tube surface is rough enough and another is spray one more layer primer on the tube(that means increasing cost)

2) I have tried sand blasting the tube, so there should be no grease and other contaminants in my opinion and also according to my observation. But I am considering using other things to clean the tube. Using epoxy do help but its cost will increase for some products.

3) If the oxide will affect the bondability?? Might ignore this factor?? actually the humidity is about 50% @30 centigrade degrees, yes, it's environmentally-controlled. As for the steel tube, it also has the same issue, also just bond rubber to steel tube. You are right, maybe we need to consider the how to erase the tube and what need to be chosen.. BUT if we do not need to do that, it's my first choice. Methylated spirits maybe good choice, I will have a try.

4) In addtion, just like Wangito mentioned above, there are so many reasons why it won't stick. So what are they? I also want to have a good undersand regarding all the factors affecting the bondability.

sandblast and then cle<an with meths, let dry for a few seconds and then use Chemlok. Tell us your experiences then.

Sandblasting alone does not guarantee a clean enough surface.....

Basically you need 2 layer coating.

1. Use chemlok 605 and let it dry for a minimum of 1 hour

2. Use chemlock 6125 on top of the 605 and let it dry for 1 hour before molding.

Note: Use TCE for degreasing and let it fully dry before coating the chemlock.

Try this and see the results

CasterMaker

Hello. My name is Jennifer McKinsey and I am a technical service representative for LORD Corporation. Chemlok 6125 is considered a two coat adhesive. This means that you must use Chemlok primer 205 on the aluminum prior to applying Chemlok 6125. The suggested procedure is to clean the aluminum, blast with 40g aluminum oxide, clean again to remove residue from the blast, and apply Chemlok 205 within one hour. Chemlok 205 should be applied between .2-.4 mils of dry film thickness. This layer should dry for 30-45 minutes at room temperature, and Chemlok 6125 can then be applied between 0.5-1.0 mils. This will give you a total dry film thickness between 0.7-1.4 mils. If you continue to experience problems, please contact me at jennifer.mckinsey@lord.com.

Jennifer McKinsey

what the dog said