Primocon vs. Interprotect 2000E?

[Maestro]

Any thoughts on priming a bare aluminum boat bottom with Primocon instead of Interprotect 2000E?

Interlux describes Primocon as "an excellent barrier to reduce pitting caused by galvanic corrosion."

It is cheaper and involves a slightly simpler application process than Interprotect.

[jralbert]

When I sandblasted the bottom, I got the paint mfr's recommendations directly from one of their tech support people. And I posted everything on the old forum. The info is somewhere in the archives of the new forum. You should absolutely double-check me because making a mistake here is not in your best pocketbook or boat interests. But I recall the Interprotect was the preferred product. But it's easy to call the mfr and get it right instead of depending on a guess here. Here's what else I remember: The first coat after sanding down to bare metal should be applied within hours -not a day or days - after sanding. Otherwise oxidation will prevent paint from sticking properly.

(and if you do make that call to the mfr - I remember they were easy to reach and friendly -- post the results here so your pals have the latest info)

see update below

[jralbert]

I had nothing better to do just now, so I dug into the archived postings here (it was an interesting process) and came up with the bottom painting steps I passed along some years ago as recommended by Interlux:

Here is the paint mfr's recommended process.
- Wipe the hull w/202 solvent to get rid of grease et al that could be driven to the surface by blasting. Make sure your Capac probe and thru-hull transducers and any other places you don't want blasted are adequately masked. I plan to tape a pie plate section over my Capac and transducers. Perhaps, the water intakes as well should be taped off.

- Sand blast w/80 grit or lower to get a "better profile". (I will probably go with soda blasting because that appears to be what is locally available - the factory prefers sand as noted but the marina thinks soda will work OK. Incidentally, the marina will sub out the work to an experienced "blaster" with whom I have spoken and who has done half a dozen M's and I have confidence in the marina painter's judgment) [NOTE: the blasting material used was actually recycled glass beads, not soda or sand]

- Brush, air blast, or vacuum off the residue. Don't, the factory cautions, wipe down with rags because fibers will be pulled out of the rags and will show thru the finish and be "ugly!"

- Quickly, go to Vinyl Lux Prime Wash, 1 coat thinned 25% with 355 solvent. Critical: this step must be done within no more than a few hours of sandblasting so the aluminum does not oxidize. Aluminum oxidizes rapidly, adding a thin protective coat to keep itself from rusting which is the beauty of aluminum and the curse of painting. This should take about 1 gal of the Prime Wash. The Prime Wash should be allowed to dry for one hour minimum, but no more than 24 hours before going to the next step.

- Apply 4 coats of Interprotect 2000E. Four coats will take about 6 gals. Minimum 40-degrees ambient air temp. Allow a minimum of 5 hrs drying time or use the "thumb print test". That is, press your thumb onto the painted surface and if you leave a print but get no paint on your thumb, the paint is ready for another application. After the first coat of Interprotect you can relax
because the aluminum has been sealed. Whew! You can wait up to 6 months, says Interlux, between coats. But when you are ready to apply the final bottom paint coats, see the next step.

- Between the last coat of Interprotect and the first coat of Trilux (if you are using another brand such as ePaint or Kolor, check those paint mfrs for recommendations) you have a tight window. Again a minimum wait of 5 hours or the thumb test noted above...and a maximum wait of 9 hours before the Trilux goes on. This means that the last coat of Interprotect and the first coat of Trilux should be done on the same day. The mfr rep explained that the Interprotect must still be curing to grab the Trilux, that's why the max 9 hour window is specified. Obviously, if the weather is really warm, you may not want to wait the full 9 hours.

- Home stretch. Three coats of Trilux which, for a 32 foot boat should take 2.5 gals. Follow paint can recommendations for time between coats. With luck, next year you should be able to get away with a light sanding before applying just one refresher coat of T'lux.

[Fastjeff]

Being basically lazy, I simply re-water blast the old Trilux 33 and lay on a new coat. Seems to work.

Jeff

[bcassedy]

Three years ago, I followed Joel's instructions with one caveat from Jeff. A PO had the bottom painted (which included painting over some pretty significant pitting). I was going to fill in the pitting after sand blasting (PC-11). Jeff advised a first coat of Interprotect 2000E which I did. Good advice. Filling the pitting w/o a coat of Interprotect would've left large areas bare and the exposed aluminum would've oxidized, making paint adhesion improbable. Did a number of coats of Interprotect (alternating between white and black so allow for easy recognition of areas needing coverage for the coat currently being applied). Finished up with 2 good coats of Trilux 33 within the time frame specified.

Bottom needs another coat of Trilux (final Interprotect showing). Will paint with 1 coat of white and 1 coat of black (same reasoning - ensuring coverage). Using Jeff's power wash and paint scheme. This is also the manufacturer's recommendation.

Bill

[Maestro]

Thanks for all the great info guys. I may call Interlux sometime but it's looking like Interprotect 2000E is the way to go.

The bottom paint on my 28 is in rough shape and getting re-done this spring. We won't be starting till April at the earliest but I plan to document/photo the whole process to add to the wealth of bottom paint info that is already here on the forum.

[jralbert]

I had the bottom blasted clean because there were years of overcoating and rough patches. Until then, the marina power washed on the annual haulout (sometimes chunks of paint came flying off) and I lightly sanded in the spring before topcoating. After the costly start from scratch/blast/follow mfr advice process, I got a baby's bottom smooth hull and my speedometer showed the difference... an almost 9 mph gain In speed (and lower fuel useage). Of course, you have to put a lot of hours and miles on to make up the cost of it all. Of course, I was crazy - I had a boat. But I could see positive results.

And a side note to Maestro: do make that call. It won't cost you anything and things change over time. Interlux may have a new product and a change in process.

[RustyBoat]

Thanks for all the great information! I have to bottom paint my 32' before putting her back into the water. I have a bunch of pitting I need to address and some of it is pretty deep. Whats the best process to fix with a welder(what wire?) or is it better to prime then use a filler(what type)?

[bcassedy]

>>> I was going to fill in the pitting after sand blasting (PC-11). Jeff advised a first coat of Interprotect 2000E which I did. Good advice. Filling the pitting w/o a coat of Interprotect would've left large areas bare and the exposed aluminum would've oxidized, making paint adhesion improbable.

I'll stand by the process above. I did use the PC-11 product after the first coat. I've power washed the boat each fall since and haven't had any of the filled points (and, lord, there were many) fail/fall out. Mixed to specs the stuff is tuff! (enough so that you can drill and tap it!). Get good adhesion and it'll last till the next time you want to blast the bottom. Definitely cheaper than hiring a welder unless you have holes all the way through. Then you may need to cut out the section and weld in new plate. Deep pitting? Go with PC-11.

Bill

[Fastjeff]

Glad to hear you have been successful with the PC-11 as well. Mine still is holding up after 8 years.

Jeff