CN24

I've read several posts regarding painting drives that told what to use and how to paint. My question is, are there ingredients(copper, or other metals) in the recommended paints that would cause electrolysis with the aluminum drive?

johnkot

I don't know if this specifically answers your question but I have been told that owners of aluminim boats cannot use the same copper-based or tin-based bottom paints as those used on fiberglass because of electrolysis. It sounds to me like you may run into the same thing on your outdrive.

Not sure what paint you plan to use. I am trying some stuff this year called POR-15. I don't know if anyone on this board have heard of it. There's a process of cleaning, prep'ing, bottom coating then final topcoat. It looks and feels very strong. Time will tell.

JK

KSFLYER1

I am having the same outdrive painting dilemna. Any other thoughts on Painting???? KS

jamess4

Previous post suggeted several methods to prep and coat for continous imersion service - you can also go to awlgrip.com to get specific part numbers - Corrosion occurs more quickly when electical currents flow accross a metallic surface,often becuase of leakage from the boat/ bad ground 12v / leakage from the marina 120v / or as a natural battery with dissimilar metals are in the proximity of each other -

Prep aluminum surfaces by blast cleaning - carefully wash with salt away or Chlorrid - wash with demineralized water ( grocery store item) wash again - you must get the chlorides out of the corrosion pits - sh@#$t your already wet - wash it again - prime using epoxy ( see awlgrip or equal). Allow applied coatings to cure, most cure schedules are based on 77 degree 30% RH - Then put you anitfoulant paint on -as long as you have the epoxy boundry layer this system will work fine This is how an Aluminm Navy Mine sweeper is painted ( your tax dollars)

Some guys get crazy about "natural batteries" - your car has an aluminum wheel bolted to a cast iron drum - last forever unless you put it in salt water - then fails quickly -

About POR-15 - this is a type of epoxy, good stuff , very low permability, hard to apply on verticle surfaces but is not a magic fix all, and it is very hard to sand. Because it matures rapidly and very often top coats of paint do not stick. Stay with coatings that have proven compatability - no such thing as magic paint - I have never used alwgrip but suggested it becuase it is readily availible to boaters, web site is decent and it is consistant with industrial painting systems were millions of $$$ are at stake not just a pair out drives -

CN24

[QUOTE=jamess4]Previous post suggeted several methods to Prep aluminum surfaces by blast cleaning - carefully wash with salt away or Chlorrid - wash with demineralized water ( grocery store item) wash again - you must get the chlorides out of the corrosion pits - sh@#$t your already wet - wash it again - prime using epoxy ( see awlgrip or equal). Allow applied coatings to cure, most cure schedules are based on 77 degree 30% RH - Then put you anitfoulant paint on

I'm not using antifouling paint. I understand the concept that if the primer is applied properly it will provide an insulation between the aluminum and any copper in the finish coat of paint. Is there any copper in the primer you recommened? The boat is lift kept but sometimes it's left in the water for several days at a time so I'm not looking for anti fouling protection, just electrolysis protection.

Poorsche

Electrolysis is not pretty--got burned by it last year from boat next to me and from marina electrical system. Make sure you've got Galvonic Isolator in shorepower system, continuity in bonding system. Pettit has some information about painting alum drives at http://www.pettitpaint.com/catalog_browse.asp?ictNbr=80

Interlux also has a fair amount of data same subjet.

jamess4

No copper in polyamide epoxy primers I suggested and I looked at Awlgrip web site again - looks like std imersion grade materials. The key is to isonlate/insulate areas you want protected by incapsulation. If you do not need an anti foulant paint then for sure get your protection with a zinc or magneseum anode ( the little thing that bolts to your freshly painted drive). Zinc will last loner in corrosive enviorments like salt water. This anode does not have to bolt directly however mercury has gone to great lenghts to provide mounting locations, make sure the threads are clean, then bolt your protection in place.

Can't stress enough getting chlorides out/off the aluminum surface, just blast cleaning is not good enough and in fact you can peen the salts into the aluminum and never know it.

You will always find corrotion problems at the intersecting contact points of painted surfaces with unpainted SS surfaces. Avoid this when possible. Washing off surfaces with freesh water helps to remove the salts, salt water is a great conductor of electricity and even a salty film that gets wet with dew each night can be problematic. Salts aslo absorb moisture and on a nice day that is 75% RH the corrosion is at work. Most important A good paint job should take a six pack of beer, a great paint job should take a case of beer and be hand delivered by Hooters girls -

CN24

James
Thanks for all the great info!!! What happens with a keg of beer?