Fixing Paint on Outdrive

[geoffr]

After being in the water for a few weeks the paint on our outrdrive has flaked off some.

After it was sanblasted I painted it with 2 coats of zinc primer ( Zinc Primer: Zinc Phosphate Yellow | ). Then painted it white with moeller paint.

Any ideas what I may have done wrong?
How would you suggest I fix up the paint? I want to get it right as our next haulout will be a couple of years out..





thanks!

[Orion Jim]

My buddy has a Beneteau with a Volvo saildrive. A couple years ago he sanded all the paint off and put three coats of Interlux Interprotect 2000e on it. He sprays a couple coats of Trilux 33 antifouling on it before he launches each spring. Looks perfect.

[Pete7]

Geoff, how long a time period between the sandblasting and the zinc primer going on?

Doesn't aluminium have to be painted almost straight away?

I have done a similar job on a stern drive, but it was roughed up with 80 grade sandpaper and then immediately painted with the zinc primer.

Previously tried hamerite on dive cylinders but it didn't stick well and the formula has since changed. It isn't what it used to be.

Pete

[geoffr]

Pete,

the Zinc primer wasn't put on imediately.. was probably a couple days.. perhaps that was the problem.

Jim,

I've though of interprotect.. but did go that way as I wasn't putting antifouling on it... but a thought as it's worked well on other metal underwater.

Geoff.

[a64pilot]

Obviously the failure was between the primer and the metal.
There are several forms of zinc chromate primer, many are spray cans, the best I’ve used for aircraft was a two part epoxy propolymide (sp) and brushed it on.
It is far superior to the spray bomb stuff.

[Elie]

Why should such problem occurs?. The st probable cause is an electrical stray current problem that starts some galvanic action with underwater equipment. Aluminum is always the risk in this case. A good anode is the first line of defense, but finding the source of the problem is a good idea.

[geoffr]

Originally Posted by Elie

Why should such problem occurs?. The st probable cause is an electrical stray current problem that starts some galvanic action with underwater equipment. Aluminum is always the risk in this case. A good anode is the first line of defense, but finding the source of the problem is a good idea.

Elie,

I'd be surprised if stray current is the problem - there are two smaller anodes on the outdrive plus one around the shaft as per the manufactures recommendation. The outdrive is electrically isolated from the engine due to the flexible coupling (Plastic). There is a ground wire to the main boat anode.

[merlinuxo]

Aluminum oxide forms very quickly and so the shortest delay possible between sanding and painting is best.
Also, it should be etched with a mild acid prior to painting with chromate.
I’d check out a couple YouTube videos before starting over.

[a64pilot]

Originally Posted by merlinuxo

Aluminum oxide forms very quickly and so the shortest delay possible between sanding and painting is best.

Also, it should be etched with a mild acid prior to painting with chromate.

How to paint an airplane, but I doubt it’s much different

https://www.aircraftspruce.com/catal...?clickkey=7822

Just read 1.

[Pete7]

Geoff,

13.40 onwards is interesting

https://www.youtube.com/watch?v=GIw_VxfzCis