# How to Apply Ospho to Aluminum Boat Hull???



## minuteman62-64 (Mar 15, 2015)

Brush/spray on, let dry and rinse off (these seem to be the directions for use on rusty metal)? Or, apply, keep wet for a period of time (this has been by experience with other metal prep/etch products), then rinse off? Or, other???

I'm experimenting on areas of my hull that apparently have mill scale causing corrosion.


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## Johnny (Mar 15, 2015)

any standard spray bottle will work fine. . . . . 
spray on, let dry and rinse off
just BE SURE to label what is inside the bottle.


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## minuteman62-64 (Mar 15, 2015)

OK, good to know. I've got a couple of those that have never been used. So, spray it on and let it dry before rinse-off or keep it wet for a period of time then wash off?


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## Johnny (Mar 15, 2015)

yep - pretty straight forward.

If you see the fluid doing the "fish eye" thing, you may need to wash
with soap or degreaser for the Ospho to work properly.
It will not remove grease or oil residue.
For heavy oxidation or corrosion, I would spray on Ospho and scrub with the green
scrub pad to really get into the surface - let dry - wash off - spray on another coat.
Let that one dry overnight as per their instructions.

*From the Ospho.com website . . . *
NEW METALS - For new ferrous or aluminum metals: remove dirt, grease, or oil; apply OSPHO, let dry overnight, then paint.
For best results, use OSPHO at temperatures no lower than 36 degrees F. Excessive dew and humidity may prolong drying time and cause powdery buildup.
Best results have been achieved using an oil-base primer and topcoat. Test a trial sample before using under epoxy or latex-base paint applications. OSPHO is equally effective for exterior and interior work alike and is highly recommended as a pre-treatment coating by leading paint manufacturers.


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## PSG-1 (Mar 15, 2015)

I always rinse it off before it dries and leaves white powdery residue, as this can interfere with paint adhesion. If you're painting, following the rinse, let it dry, then, wipe down with acetone. Then, one very thin coat of zinc chromate. Then your primer and/or paint.


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## minuteman62-64 (Mar 17, 2015)

Been doing some work on my bunks, so, had the boat up off the trailer. Buffed the areas where the bunks sit. Yesterday applied ospho as per advice.
Bottom photo shows buffed area on left and untouched area on right. Top photo shows same areas, with buffed area on left treated with ospho.

Looks like the ospho is doing the job. I'll continue with the remainder of the bottom, in increments, after I get the boat back sitting on the bunks.


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## minuteman62-64 (Mar 18, 2015)

Did some test areas topside on the hull. See photo. Ospho application areas are under blue tape strips. Two areas on right were mechanically prepped, one with Scotchbrite buffing wheel and one with more aggressive paint stripping wheel. Area on far left had no mechanical prep.

Ospho took off the "flowers" on the area with no mechanical prep, but didn't seem to give the overall etching effect as on the areas with mechanical prep.

I will continue the remainder of the hull, in phases, with mechanical prep (buffing/wire brushing/sanding/etc.), followed by a wipe-down with denatured alcohol and then spray on Ospho.


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## Johnny (Mar 18, 2015)

Ospho is not designed to REMOVE corrosion - or make a smooth paintable surface.
It is only designed to NEUTRALIZE the rust or corrosion so after a suitable primer
is applied and after it dries/cures, it forms a moisture tight barrier between the metal
and the topcoat of paint. The topcoat will be the one that actually provides the protection 
to "retard" any future rust or corrosion.

You are on the right track to physically and mechanically remove any surface corrosion
first - - - *then*, use the Ospho prior to applying your primer to actually get into the pores
of the metal and completely kill any corrosive salts.


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## minuteman62-64 (Mar 18, 2015)

Actually, when it comes to painting, I'm in the camp of most of the owners, of similar boats, that I've chatted with at the San Diego Bay launch ramps - "... the reason I bought an aluminum boat is so I wouldn't have to deal with that s**t."  

The diagnosis of my hull issue, on this and other sites, is failure of the builder to remove mill scale. So, that's my objective in the buffing and Ospho application. I'll monitor the treated areas over the next few years to see if the treatment had the desired effect.


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## Johnny (Mar 18, 2015)

:LMFAO:


> *"... the reason I bought an aluminum boat is so I wouldn't have to deal with that s**t."*


 :LMFAO: 


*B - O - A - T* = *B*ust *O*ut *A*nother *T*housand !!!!

Since around 1968 or so, I have owned dozens of boats.
Fiberglass, wood, aluminum - - - They ALL will give you FITS !!!
It is part of the Nautical World. . . . Welcome Aboard, enjoy the habit and HAVE FUN!!

Hang around, read, watch, ask questions.......
address your boat issues BEFORE they become PROBLEMS !!


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