Jazman wrote:I could feel these rough bumps, I thought they were barnacles... They were NOT! They are corrosion blisters from UNDER the paint... I need to decide what to do. what do you think is the CHEAPEST way to do it? I have attached a several pics of the bottom so you can see what I'm dealing with.Bill
Bill: I looked back at my post from last spring on bottom painting...found it and am re-posting it here.
(site admin note: when I went back into the hull/painting thread I could see only posts from the last 6 months. Took a while to find the post via search - but, whew, it's done))
Jeff isn't kidding, the only way to do the bottom is to do it right. Once the right way will last many years. At the outset, I do not think paint per se is your principal problem - I think you may have gotten the wrong paint, one with lots of copper in it. Or you have a failed isolation situation. Or wrong/insuffcient zinc. There are many recent posts here on those scenarios and some horror pictures. That is where I would look first because I think you could have a naked bottom (boat, that is) and still not wind up with the corrosion you are encountering.
If you can do the job yourself, you can, of course, save some money. Proper prep is key. The materials are not out of sight expensive. As far as paint brand is concerned, either Interlux (Trilux) or ePaint are ok. I have used both but have migrated back to Trilux. Kolor paint claims to do the job -- and it may -- but I haven't tried it.
What I have done, with help from others on the forum, is to dunk test strips of aluminum in the water for months and compare results between Trilux & ePaint ZO No Foul. First year, ePaint did a better job of fight barnacles, the next year Trilux changed its formula apparently and was the clear winner. After I repainted the bottom (at a hefty expense) last spring, Trilux showed good results notwithstanding that the boat sat for weeks without moving. Trilux uses a derivative of copper (not straight copper) as the anti-foul fighter and ePaint uses hydrogen peroxide. Either approach makes sense.
OK, here is the paint procedure per the Trilux support guys:
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- 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 IU have confidence in the marina painter's judgment)
- 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. That coat will keep paint from sticking and everything will peel off, leaving you despondent and in tears. 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 apply a single coat after a light sanding. I plan to make the final coat a different color so wear will be obvious.
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There are a number of other useful posts on this subject on the board. I am not the reigning expert on paint, so do a little research while you have the time and the weather favors staying indoors.
Joel Albert, Potomac MD
"Charlie B" - 1988 32' FBS
Twin 318's/FWC/16x15 nibral props
docked Deale, MD
