attaching carbon fiber panels to a mild steel frame

[TDrax]

I could use some advise on how to best prepare a mild steel frame for attaching a carbon fiber panel. The panel will sit inside the frame and carbon and kevlar tape and epoxy will be used to bond the panel to the frame. I have read that degreasing, then etching for 10 minutes in 15% hydrochloric acid and then rinsing will prepare the metal. Is bonding directly to bare metal best? I would prefer to coat the metal with something that protects it from corrosion and provides a good base for the epoxy.

Thank you

 

[MintJulep]

How strong does it need to be?

The joint will only be as strong as the weakest bond in the load path.

If you paint the metal, then glue to the paint the weakest bond will most likely be paint-to-metal. Not too strong typically.

 

[GregLocock]

The epoxy is a reasonably good paint in its own right.

We used to do a mechanical abrasion (180 grit), wipe with Methyl Ethyl Ketone, dry, join. You may find that you are not allowed to use MEK.

I haven't come across an acid etch process before.

I'd paint over the completed item, for the reasons MintJulep gives.



Cheers

Greg Locock

 

[MintJulep]

I've seen acid etch recommended for stainless and plastics with low surface energy. Seems like overkill for mild steel, but probably wouldn't hurt.

 

[CoryPad]

Acid etching, also known as activating, is a common pretreatment for steel parts prior to coating.

You don't need a coating prior to epoxy - it will adhere very well to bare steel. You can use epoxy-based paint to coat the entire assembly if desired.

Regards,

Cory

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

 

[corrosionman]

It all depends on the required bond strength of the fixing . The surest method is to shotblast prior to use of epoxy adhesive. It will also be the best preparation for painting. Cheers D W