Diesel tank loose

[F51]

My 70 gal aluminum fuel tank has come loose. When I installed it 18mos ago, I epoxied it with West System and cloth, but the tabbing on the tank has come loose. The hull attachments seem ok. I wonder if I did not properly prep the aluminum. I scuffed it with sandpaper and thought that would make a good bond, but apparently I was mistaken. Now I have a much more difficult repair job because of limited access. I want to do it right this time. What is the best way to get the bond between the epoxy and the aluminum?
Thanks.

[Dsanduril]

West/Gougeon recommends an aluminum etch to get a good bond. Their product #860. I suspect other etching could be used, but for a small job the cost probably isn't too great. I've had some success with this, but probably haven't put the load of anything close to 50 or 60 gallons of diesel sloshing around on my joints, so don't know if it would be effective for your tabbing.

[noelex 77]

It's difficult to good long term structural bond between alumininium and fiberglass.
Is there another way ou can secure the tank?

One reason why epoxy does not stick well is the immediate formation of an oxide on the aluminium. If you sand the aluminium while it is covered in wet epoxy the air does not reach the aluminium and the bond is much better.

Wear old clothes

[DeepFrz]

This is the way I would install an aluminum tank. No coating, no foaming.

How to Install an Aluminum Fuel Tank : Boats, Yachts - Maintenance Repair and Troubleshooting