Lord Adhesive failure, any advice?

[jtiii]

I was gluing 2" aluminum angle to acm to make returns. Used Lord's 406/19 (not expired). Lightly scuffed the angle and wiped it with ispropyl. Same for the acm. Squeezed out a mixing nozzle's worth first to ensure full mix. Clamped for 24 hours. Today I went to move the sign and the pieces snapped off with not much force. It mostly but not exclusively failed on the angle side. The adhesive is cured.
I've used Lord's a few times before without issue but this is my first time making returns and my first time experiencing failure. Can anyone tell me what I did wrong? As always, the client wanted this up yesterday

 

[davison]

Maybe drill some small holes in angle to give the glue something to lock into.

 

[netsol]

Jtiii
Glues fail in one of two ways, adhesion (the ability to stick to something else) & cohesion (the ability to stick to itself). Yours seems to have failed both ways, leading me to think either it was expired, or, perhaps got contaminated by a coating on one of both surfaces you were trying to glue, which did not come off completely when you wiped down with alcohol?

 

[jtiii]

Jtiii
Glues fail in one of two ways, adhesion (the ability to stick to something else) & cohesion (the ability to stick to itself). Yours seems to have failed both ways, leading me to think either it was expired, or, perhaps got contaminated by a coating on one of both surfaces you were trying to glue, which did not come off completely when you wiped down with alcohol?

Interesting - I just looked at the sign again and the adhesive on the acm side is hard while the adhesive on the aluminum is soft enough to smear with my finger. The tubes expire May 2nd so I'd like to imagine that's not the issue. I can try cleaning them with acetone and then 100% isopropyl but I think even though it will make the sign not as pretty I'm going to put small rivets through the face as well as regluing them

 

[Boudica]

There's another thread on here about cleaning aluminum with vinegar... Maybe try that on the aluminum? Just following out of curiosity, thought I'd toss that out there.

 

[netsol]

Sure, you clean glass with vinegar.
Seems like a good option

 

[jtiii]

I decided to clean it with acetone and then really clean it with a 36 grit sanding disc there's going to be a whole lot of mechanical adhesion where before it was all very smooth. I had given it enough tooth for painting but not much more. Also for grins I did drill some small holes as davison suggested; the lord's squeezed up through and I flattened it to make little "rivets". There's going to be no force acting on these and they're not structural so hopefully it's sufficient.

I just was shocked at how easily it failed especially since for prep Lord's just says "Remove grease, loose contamination or poorly adhering oxides from metal surfaces. Normal amounts of mill oils and drawing compounds usually do not present a problem in adhesion". It doesn't even mention abrasion. I guess the only other thing I can think of is that I just wasn't using enough.

Thanks everybody!

 

[netsol]

You said it was close to expiration date.
I went ro website and red the data sheet
It has to be stored below 80 degrees, but SUGGESTED between 40-50 degrees
I imagine you didn't keep it in the fridge, so it might have broken down chemically

 

[jtiii]

You said it was close to expiration date.
I went ro website and red the data sheet
It has to be stored below 80 degrees, but SUGGESTED between 40-50 degrees
I imagine you didn't keep it in the fridge, so it might have broken down chemically

Thank you for checking that. It was 60-70 where it was stored but anything's possible!

 

[netsol]

I have had the same experience with various epoxies, measure as carefully as possible, mix thoroughly, and they still never harden properly and achieve full strength.

PC 7 always told us to have a "sample batch" so you could verify it had hardened completely before handling your finished piece

Lately, (the last few years) we mix a test batch of all new adhesives before using, to see that they harden properly. MANY DO NOT, and go directly to the garbage

I blame this on old, trusted names using chinese co-packers, who have zero quality control

 

[netsol]

I just ordered some lord's, it looks like a great product.

 

[jtiii]

Prepainted aluminum paint however will not, and the glue will stay stuck to the paint and the panel will fall off in the oven...

Ouch I'm guessing that knowledge doesn't come from book learnin'

 

[jtiii]

That aluminum does not like it has been scuffed or cleaned in the least! We either lightly grind or sand with 80 grit before cleaning and glueing.
It also looks like there was very little glue applied

I wiped it down with acetone and then 100% isopropyl. Yeah I definitely didn't scuff it well enough—I scuffed it with way too fine sandpaper. Especially since Lord's themselves just says nothing about scuffing metal (or even doing a thorough cleaning fer chrissakes!) I thought I had done enough prep.

Surface Preparation – Remove grease, loose contamination or poorly adhering oxides from metal surfaces. Normal amounts of mill oils and drawing compounds usually do not present a problem in adhesion. Most plastics require a simple cleaning before bonding. Some [plastics] may require abrading for optimum performance.

It also looks like there was very little glue applied, and it was nearly smashed too thin

I wasn't sure how much glue to apply so that was one thing I figured might have been an issue. Other than getting the 406/19GB how do you keep the glue from getting squeezed too thin?

 

[Notarealsignguy]

Don't push too hard. I'm sure they make spacers or you could use feeler gauges if you really wanted to follow the rules but you'd probably be the only one on the planet doing that. Aluminum is naturally a PITA to get things to stick to. As mentioned, sand with 80 and then add holes for it to weep into is your best bet

 

[Scotchbrite]

We sand the paint off before gluing. As others mentioned, we don't clamp but use weights (usually old transformers) to hold the pieces in place. I'm pretty sure we were told at one point there needs to be a little bit of space/gap to allow for proper curing of the glue.

 

[a77]

Make sure you email Lord and get their comment on this too.

 

[visual800]

you have got to go down to bare aluminum on the acm, you cannot glue LORD to paint scuffed it has to have the paint off

 

[Notarealsignguy]

Why sand the paint all the way off? That paint will probably adhere better that the adhesive ever will. It stuck to the paint, the problem was on the raw side. You realize that in cars, the windshield urethane goes on the paint and they are integral to passenger safety.

 

[rjssigns]

Has anybody tried panel bond for auto body? It's better than welding but the metal has to be ground free of paint. OEM's have been using it for years. My 1981 Mercedes used it on the front fenders. Beastly stuff.

 

[jtiii]

Don't push too hard. I'm sure they make spacers

I don't really understand why the GB option is not more ready available (at least not from Wensco and Grimco) as that sure would simplify clamping.

ETA: GB stands for glass beads - they're in the adhesive and ensure a sufficient thickness