Sanding to bright Aluminum

[LCR]

I am 2 days in, and I have the roofs and sides of my Marionette 32 sanded. It is going quicker now. I tried an angle grinder and flap disk, which instantly gummed up. I tried a SS wire wheel, which worked great, but fell apart quickly (made in USA 40$, wore a welding hood). I tried a belt sander, which gummed up, and fell apart quickly too. I tried wetting the surface with the belt grinder, and the belt fell apart quicker. I then tried the angle grinder and 60 grit flap disk, and a hose of water. That seems to be the winner. I did the whole top with 1 disk. I then found a 40 grit disk and switched to that. Much better. I can push as hard as I want, and no gumming up.

About 8 years ago, I had no time, and lightly sanded, and put on some Brightside. That is now horrible, and cracking. The original off white paint was also cracking, so I felt it needed to go. The orange/toffee primer seemed mostly good, but getting the paint off and leaving the primer did not seem practical, or a great idea. The paint guys really wanted bare aluminum. The Brightside paint sands off super easy relative to the original (I think) off white, which makes me wonder about Brightside.

Questions...
So, how much are people paying to get sand blasting done, how long does this take?

Also, I'm priming with Interprotect 2000. The challenge I have is with some of the seams. The angle grinder/hose is great on the wide open flats, but misses some of the cracks/joints. I will try wet sandblasting, and the wire disk. Am I going overboard worrying about this? If it is still sticking, can I prime over the little bits? The seams are filled with a grey body fill, with no primer underneath. Is that original? In a lot of places the puddy has corrosion under it, which is setting me off a bit.

[jralbert]

Can't address all the items you raised but just want to offer this. When you sand to bare metal, you must apply primer (the correct primer,. of course, for the material you will use to finish up) within just a few hours or the aluminum will start to oxidize. When it does, the primer and everything over it won't stick long. Lots of labor and money down the tubes. From your description, there's no mention of priming once you get down to bare metal.

I had the bottom sandblasted and wish I could recall the cost. They used glass beads. It was about a 7 hour job after which the yard immediately began spraying to get in that first, all-critically important barrier coat of primer. Once that was applied, we were totally relaxed about getting on the other coats. The Paint mfr has tech folks happy to advise you - thatg's what did and followed their advice.
Good luck with a big project.

[BlueSkye]

I use zinc chromate in a spray can. First vinegar spray then that washed off with distilled water. It is green.

Used to buy it from my marina but now that is outlawed. Only supposed to sell it to professionals. The workaround is to buy it on Amazon.

[LCR]

Thanks for the feedback. I plan to do a final light sanding once I have all the paint and accessories off, and then paint. The timing will be an issue for sure. I will likely do it in separate bits. I have to re-read the primer instructions; I thought it had timing issues too. I have Alodine, supposedly a wash, which I will use in the seams. I also have to be ready to do more sea trials, as soon as my help recovers from a cold... so that is presently restraining me from starting painting.
7 hours sounds great for the "bottom" was that rub rail down, or below the water line?

[LCR]

Pics or it didn't happen.. it took 4 days, the first was really no progress, just learning. I will need another day to take all the fittings off, and re-sand for painting. Hopefully I can find a week this fall.

[Tracy]

I had my 32 bottom sand blasted last year for around $2500.
I had my entire 28 sportsman done in 2020 for around $5000.
100% worth the cost to me as I just don't have the time or desire to spend weeks sanding.

[Knotty]

https://speedcoat49.com/

No primer or sealer needed.

[Fastjeff]

That stuff sounds good enough for me to try it on my kayak. (I emailed them.)

Not sure about their claim for using on bare aluminum without etching first. That surface layer of aluminum oxide that forms immediately after paint removal is very slippery.

Jeff

[Knotty]

It’s a two part epoxy/paint so it should adhere to the aluminum very well.

[jralbert]

It has to have a primer coat..refer to Jeff's post. after primer, it will adhere as expected.
UPDATE: If this paint contains a primer and is applied immediately after sanding (within a few hrs), you can beat the aluminum oxidation time constraints