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Aluminum vs Salt Water
Posted: Sun Mar 06, 2005 6:40 pm
by scott vos
I am just beginning my first major Mod installing a marine head and I will be fabricating some 1/4" aluminum brackets and a base plate for the head to mount to.
My question is , after I have fabricated the above mentioned should I be primeing or coating the alumium with something prior to the installation, Or is aluminum safe to leave in its raw state (interior instalation)????
Any help with this will be much appreciated.
Sincerely
Scott
Posted: Sun Mar 06, 2005 6:52 pm
by waternwaves
Because of the location and the amount of caustic chemicals for cleaning.
I dont recommend aluminum inside the head...
But if you must, a 2 part epoxy garage floor paint, with suitable primer.. (for aluminum probably the best would be the dupont car primers.)
you will be better of with a white Polyethylene baseplate inside the head and the aluminum under the floor.
BTW.....the only sealants I have found that work well with PE is the 3M 4200/5200, and the GE Silicon seals.....
BAthroom chemicals are hard on aluminum....lol
Posted: Sun Mar 06, 2005 6:55 pm
by baldbaby2000
It seems like anodized aluminum might be a good choice.
Posted: Sun Mar 06, 2005 7:43 pm
by waternwaves
Anodized aluminum is a typically a mill finsish specifically for corrosion inhibition... Looking at my old reynolds aluminum supply catalogs... and corrsoion keys for aluminum. Typical cleaners include... ammonium cloride causes pitting, calcium choride causes pitting, calcium hydroxide causes pitting, hypochlorite with any liquid present is not good either... with the electro finishes, anodyzing, alodyne, etc. anodizing will reduce the attack rate....
so the important thing is to totally prime and epoxy seal the aluminum for best service life. most of the corrosion rates once through the coating, are typically in the .005 to .020 in/year... at temps below 100 deg. F so a good cleaning and moisture removal in the fall should prevent most of that.
There are good reasons Ob manufacturers coat the aluminum component of an outboard exposed to sea water...
Posted: Sun Mar 06, 2005 8:00 pm
by Don T
Hello:
We used zinc chromate on our aluminum parts but they weren't slated for salt water.
epoxy paints.
Posted: Sun Mar 06, 2005 8:15 pm
by waternwaves
The problem with zinc coatings and acids and caustic cleaners is that it is fairly rapidly consumed and zinc coatings don't take a lot of surface wear (from the mechanical cleaning)... The multicoat epoxies provide a chem barrier to slow down electrolysis..and are hard enough to stand up to most non metallic abrasive scouring pads. Rustoleum, Amercoat and many other manufactures put out excellent two part epoxies.... (your mileage may vary, and the determination of merchantablility for a particular purpose is not implied. dealer add on's not included. subject to stock on hand, Vin numbers available at the dealer.........
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