Sandblast on a 16' Alumaweld hull- thoughts on restoration

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alumioforte
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Sandblast on a 16' Alumaweld hull- thoughts on restoration

#1

Post by alumioforte » Mon May 13, 2019 6:21 pm

With today's aluminum pricing, we get so many people sticker shocked at the thought of a new boat.

Some food for thought, your old hull may not be so bad.

A good thorough sandblast, will reveal any corrosion or cracks. From here you have a totally workable surface to perform replacement welds or modifications on. Often you can structurally end up with a better than new result.

From here, you can wet paint or even better powder coat it. New floors and stickers, and your refit hull will be good to go.

Just a thought- something to consider if a new build is out of reach!

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kmorin
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#2

Post by kmorin » Tue May 14, 2019 1:15 am

alumio,
a full etch is much MUCH less cost and will show more than blasting since the blasting media will peen way too many imperfections. Better to have the acid reveal a uniform color, uniform imperfection reveal and to leave the metal ready for most paint systems?

Blasting imparts so much energy to the surface that uniformity is almost impossible without a blaster/tech/hose man who really has experience. I'm pretty sure anyone can afford a couple hundred bucks in a few bottle of Zep-a-Lume and some garden hose rinse? But the cost to gear up to blast is not nearly as casual!

I don't think the idea to strip and reveal the hull's state or status is - invalid. But I surely can't agree the cost to blast is worth the money unless you have planned a repaint within a day or so?

Corrosion and pitting will not be well displayed by blasting. Why? The blasted surface is a series of tiny pits and they will clean out most corrosion- however they leave a uniform appearing; mottled surface. On the other hand acid etching will leave the pits to stand out- glaring... not camouflaged by the surrounding pitting of the blast media.

I'm still not willing to buy into powder coating an entire hull, until there's more water under that bridge? Only recently have there been ovens to accommodate an entire skiff, and prices offered weren't really competitive with paint.

So, if someone has an older welded skiff; the most effective reveal is to etch. Then any flaws or faults can be seen most clearly. Blasting may help see cracks... not common in a well found welded aluminum boat... but corrosion and other problems are covered by the surface treatment's mottled coloration.

I fully agree that old skiffs may be 'babies' in life and with some well informed handling they can be cleaned, repaired if needed and live long and serviceability lives if they're well tended.

Cheers,
Kevin Morin
Kenai, AK
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gandrfab
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#3

Post by gandrfab » Tue May 14, 2019 4:36 am

From what I have seen sandblasting alone does not leave a clean weldable surface.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#4

Post by alumioforte » Wed May 15, 2019 12:50 am

Kmorin,
I'm referring mostly to hulls that have paint on them already- yes if its bare aluminum, no need to sandblast.

In terms of powder coat- it depends which shops you talk to. In Seattle, powder coat is very definitely half and sometimes better than half, the cost of wet paint. In terms of water under that bridge, SafeBoats has had boats in the water since 1990 that were powder coated- and still looking good. I know that for a fact because the CEO himself told me that. The cost of powder coat is going to depend on what kind of experience those shops have.

Tracker Boats- one of the largest aluminum boat builders in the world by volume- powder coats their boats. If that helps. To hide the secret they call it "diamond paint" but its nothing more than powder coat.
http://www.youtube.com/watch?v=gG9AiCIH5T8

kmorin
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#5

Post by kmorin » Wed May 15, 2019 12:32 pm

aluminforte, OK i see what you were suggesting. Yeah an old paint job will come off best with a sand blast, even though the cost might be North of chemicals and acid washing. Especially if the boat were going to be re-coated, especially powder coated.

Did not know about the boats you mentioned as powder coated, and didn't know the cost was down to 1/2 of painting! The only few posts we'd had here (re: powder vs paint) had quoted some pretty high costs - but that has been several years, don't recall exactly?

So are you saying someone with a 10-15 year old Pacific, Specmar or Workboats skiff could have the boat stripped, blasted and powder coated for 1/2 the cost of a paint job - in the Seattle/Puget Sound area?

what is a conversational cost per foot for this type of process?

Thanks for the clarification.

Cheers,
Kevin Morin
Kenai, AK
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#6

Post by alumioforte » Wed May 15, 2019 8:19 pm

Typically the cost for a single tone ( one color) inside and out costs $85 per boat foot, so an 18' skiff, for example would be $1,530.00. That cost is strictly a sandblast, duraprime, and topcoat. Repairs etc would happen after sandblast but before prime.
A couple notes of import:
1. Its important to use DuraPrime, or a similar powder primer that has no zinc in it. Often electrostatic coatings put zinc ("zinc-rich primer" as they call it) to enhance conductivity. That in my opinion is an electrolysis risk, (anodes often are made of zinc, because zinc is more conductive than aluminum) so we believe its important here to use epoxy based, zinc-free primer. You have to use a bit more material because it has less transfer efficiency from the spray gun to the hull, but the cost is negligible.
2. it is important to note that when powder coating, the entire hull must go into a curing oven. This means that all plastic or items that could potentially melt, must be removed. So its best for a stem to stern refit and not just casual "spring refresher" projects. The good news is, most foam including styrofoam can take up to 400F heat so that is usually a non issue.
3. On the foam subject, we've seen cases where the boat had leaks and the foam was waterlogged. By leaving the boat in the oven at 220F just above 212 which is boiling for an extended period (2, 3 hrs) , all the moisture boiled and converted to steam, evaporating out of the relief holes cut. This was cheaper than cutting out and putting new foam in. With the foam now dry, we then sandblast, reveal the water ingress points, repair those, and get back to new.
4. Sandblast media can include 80 grit garnet sand (most common) or less aggressive types including walnut shell, glass bead, or plastic beads. Glass bead has more of a polishing effect than a cutting effect and is good for restoring stainless steel.

Its an interesting subject. Being done in europe for so long, I expect we'll see it becoming more prevalent here, especially as more shops get equipped to handle bigger and bigger boats in their curing ovens.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#7

Post by kmorin » Thu May 16, 2019 12:50 pm

Alumio',
great post, thanks for all that info. Living off the beaten path, we don't have the larger ovens locally and most people are using vinyl side panels or maybe a painted topsides panel; most of the boats I've been involved with recently have been larger- >25' LOA.

Good info though, for the readers of the Forum who are in the Puget Sound or PNW who might be considering work on their hulls? There could be an entire business based on recovering used Lunds, Gregors, and Starcrafts that might be had for little money? (Don't know market values) and then stripped and touched up in the metal work (might require some riveting or welding?) and then powder coated to refinish and then resale?

Thanks for the detailed info.

Cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#8

Post by alumioforte » Fri May 17, 2019 12:03 am

https://photos.app.goo.gl/hLA5SPu9zERH5G1E7
Here is a picture of an entire sandblast on a Specmar boat today.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#9

Post by Chaps » Fri May 17, 2019 10:00 am

For what it's worth I get quite a few fibrglass boats in for bottom painting that have powder coated aluminum engine pods that show coating failure (peeling). I don't think powder adheres very well to aluminum, particularly in a moist or submerged application. IMO its an oversold technology, either that or the shops that apply it aren't doing something right.
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#10

Post by kmorin » Fri May 17, 2019 10:53 am

What do the major outboard makers use? Are all those engines powder coated of some type? I've seen them last pretty well but then have a nearly new little kicker where there's extensive lifting and corrosion under the coating; especially around areas where the intakes and 'zincs' are located!

Interesting topic to discuss but unfortunately the guys doing the work won't be all that forthcoming if their coatings fail? Bad ad? Wish more members had reports of powder coated equipment/boats/lower unit repairs... to form some sort of "learn from" experience?

Alumio, how many years experience have you got with powder coated hulls? Are they work in your shop or are you watching other services/shops around you and reporting? I'm interested to learn but not planning to haul a hull that far to test!

cheers,
Kevin Morin
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#11

Post by alumioforte » Sun May 19, 2019 11:52 pm

Like anything, powder coating is only as good as the prep work. Powder coating is basically micro ground particles of plastic, that you put in an oven and it melts.

If you see powder coat peeling or flaking, it is simply because they didnt sandblast the substrate.

Imagine bolting a peice of UHMW plastic to the bottom of a hull. If the UHMW falls off, its not because the UHMW was bad, its because it wasnt fastened properly.

Unfortunately, poor training in both wet paint and powder coat, and the desire to do the job faster / cheaper, many mfrs. unfortunately choose merely a chemical wash prior to spraying.

Here is a video that sums it up well. https://www.youtube.com/watch?v=avTpqL7fFoY

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#12

Post by alumioforte » Sun May 19, 2019 11:57 pm

At the end of that video, you can see that even at 1,400 PSI of pull on the powder coat on the aluminum peice, it still doesnt come off.

Therein is the difference of sandblasting the substrate vs. chemical cleaning.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#13

Post by Chaps » Mon May 20, 2019 8:51 pm

Couldn't agree more when talking difference between blasting and chemical etch for any type of coating on aluminum however the video test procedure doesn't take into account the effects of time and exposure to UV and moisture that eventually takes its toll on the typical powder coat bond.
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#14

Post by alumioforte » Tue May 21, 2019 9:14 pm

Any Tiger Drylac or Cardinal brand powder coat meets AAMA 2604 standards, which is a salt spray / south Florida UV exposure test.
Zolatone doesnt meet AAMA 2604, I'm not familiar with other paints.

Oh one more case in point. Did you know BMW and Tesla car bodies are powder coated?

There is powder coat and there is powder coat. The key is the prep, process, and formula. There are polyethylene, polyester, and TGIC formats so saying "powder coat sucks" is like saying "paint sucks" becaue "paint" could mean anything from rattle cans to watercolor to latex to 2 part urethane.

Anyway, here's to long-lasting beautiful aluminum coatings :beer:

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#15

Post by gandrfab » Wed May 22, 2019 5:02 am

Th buyer beware part is easy to understand after seeing so many aluminum boat tops powder coated with inferior products and craftsmanship. Bubbling, flaking and chipping.
If someone is buying a used boat, car, railing, fence...anything that has been powder coated is there anyway to tell the good from the bad?

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#16

Post by kmorin » Wed May 22, 2019 12:21 pm

alumio,
like paint jobs on metal boats, unless you're in the loop on who did the work, you're left to speculate on the results? Similar to welded aluminum boats years gone by- before there emerged name builders whose work stood up and was eventually shown to be better quality than other builders' boats..... powder coating seems a like it has seen poor performance in many instances?

If this was due to age of the product line in the market, and combined with poor install or inadequate prep processes? It won't show up - no body seems to care to document the lineage of the coatings that failed.

So powder coat will have to spend some time- proving itself to be worth the effort. So did welded aluminum boats... but there are thousands of boats out there with avoidable problems due to build or post build problems still done improperly by very name builders and manufacturers.

Or as one very large West Coast/Puget Sound builder told his client of a $250k boat that was a couple months old.... "That corrosion is just normal for welded aluminum boats (!!)" After I helped the new owner etch his boat and the corrosion stopped, the builder still claims that corrosion in their brand new quarter million dollar boats : " .... is normal".

Will be interesting see how the correctly installed powder coatings stand up?

Thanks for posting, and please take time to follow up - it sure helps a reader here to be more informed on both sides of these aluminum related developments.

Cheers,
Kevin Morin
Kenai, AK
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#17

Post by alumioforte » Wed May 22, 2019 2:43 pm

All good thoughts. I'd say the Tracker Boats and SafeBoats, who do powder coating right, are the answer for me, because they not only have the volume of boats, but the length of time theyve been doing it. Companies that big must take their coatings seriously.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#18

Post by gandrfab » Thu May 23, 2019 5:52 am

Size of a company does not guarantee quality.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#19

Post by kmorin » Fri May 24, 2019 12:39 pm

alumio, I agree with G&R that company size isn't the biggest/best criteria for judging a company's compliance with good practice!

I've sure seen some big name built hulls that were having totally avoidable problems - relating to coatings. So I can't see larger manufacturing companies' efforts as necessarily best practice just based on size.... but I could agree if both of these companies' boats have weathered well, and their powder coatings were in good or better shape than paint after a few years that would be a good report on powder as a durable top coat.

I'm not sure I've ever seen either builder's boats in person so that eliminates me from a real world experience with them.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#20

Post by Chaps » Fri May 24, 2019 10:55 pm

I work on Safe Boats, I can't say I've ever seen anything on them yet that has been powder coated. The topsides are typically bare with some vinyl graphics, the collars are hard foam coated with polyurea and the bottoms are epoxy overcoated with bottom paint. What are they powder coating?
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alumioforte
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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#21

Post by alumioforte » Sun May 26, 2019 8:32 am

Il send some pics Tuesday. We have 2 jobs in the shop right now from you guys for the Tacoma yard.

Also Life Proof does it a lot here's a pic of a recent one that was coated stem to stern top to bottom. Also we do their 10/18 Ribs.

https://www.lifeproofboats.com/23-25centerconsole

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#22

Post by alumioforte » Sun May 26, 2019 8:40 am

Here is another pic of a RIB for LifeProof, silver polyethylene

Image

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#23

Post by alumioforte » Sun May 26, 2019 8:45 am

Image
Wooldridge also extensively powder coats.

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Re: Sandblast on a 16' Alumaweld hull- thoughts on restoration

#24

Post by alumioforte » Sun May 26, 2019 8:52 am

Here is also Umpqua boats, who powder coats. There are many others.

Im certainly not saying everyone should powder coat - just that there are many highly reputable builders in the industry who are very happy with the results that have switched over from wet paint.

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