Affixing SST to Al

[bama01]

I would have never thought in a million years it would be this hard to epoxy SST to Al...

I am trying to affix 301 SST to 6061-T6 Aluminum. The surface area is 1 SQinch. I prep both surfaces by sandblasting and then I clean with acetone. I apply the products to the letter of the law, I let it dry for days.
I have tried everythng under the sun, but the parts come apart way too easily. I've done epoxies specifically for metal, I've tried Loctite, extreme adhesive, superglue types, general epoxies... Actually the Extreme Adhesive 300 worked fairly well, but the bond failed after a few months passed.. What am I missing? What else can I try? What other surface prep can I do? Are these metals just not meant to be glued?

I welcome your thoughts! Thanks. Jim

 

[CoryPad]

I suspect your epoxy to aluminium interface is weak. There is a lot more you can do to the aluminium surface prior to epoxy application.

Go to ASSIST-Quick Search, the US military's document service:

http://assist.daps.dla.mil/quicksearch/

Type MIL-HDBK-509 in the Document ID box and click submit. This document, MIL-HDBK-509 Cleaning and Treatment of Aluminum Prior to Painting, is very helpful with surface preparation of Al.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[IFRs]

You could try a methyl methacrylate (spelling likely wrong) tape - which is used for road signs. The thermal expansion differences between the two metals may create significant shear stresses and bond failure. MMA comes in tape form which may have more flexibility

 

[unclesyd]

As posted by CoryPad the biggest problem is going to be on the Al side of the joint.

Here are couple of approaches you might take.

Go to a big marine supply store and look for a West System kit for bonding Al. While their look for an Al etchant.

At a big box store look for a two part structural epoxy adhesive that is heat cured. If no one has it you may have to use the Internet.

Have everything ready to go.

To prepare the Al do the normal degrease and clean. Depending on quantity Using medium weight rubber gloves I would use a ScotchBrite maroon pad to abrade the surface while keeping pad soaked with any Phosphoric Acid cleaner (Weedac, Ospho, etc.) diluted three acid to 1 water while abrading. After abrading rinse the part in freshly poured bottled distilled water if possible.

As quickly as possible.

If you have an Al etchant, treat the part as per instructions and then apply the adhesive per instructions.

Normally on this type joint one would use a sealant and a mechanical fastener.

What type environment will the joint see?

Any temperature?

 

[bama01]

Well, here's the thing, the epoxies I've tried, all of them, the failure comes from the epoxy coming off of the STAINLESS STEEL.

This is an indoor application, no temperature swings.

 

[MadMango]

Probably need a primer for the AL. In the past, I have had good results with adhesives from Sika.

http://www.sikacorp.com/

 

[unclesyd]

I was going to mention the SS in my previous post but layed off because normally the Al is the bad actor, but SS can be aggravating at times.

Check for the same systems as mention before.

Follow the same prep as used on the Al with the exception an added step where the bonding area would benefit from an abrasive blast or even glass beads. I would still clean after blast with SB pad with the Phosphoric Acid.

As I stated before everything need s to be ready to carry through with the whole process once started.

 

[strider6]

have a look at this page on joining aluminum:

http://aluminium.matter.org.uk/content/html/ENG/default.asp?catid=47&pageid=2144416963

maybe you can find some good hints

hope this help

S

Corrosion Prevention & Corrosion Control