Hull Corrosion on Hewescraft 220 Ocean Pro

[kmorin]

bfetcho,
I agree that Hewes does seem to want to solve problems, so I'm glad to hear you contacted them and they're working to learn more. That's different than having a builder basically tell and owner that they're on their own solving a problem.

As to KO? I'd say it WAS Zep? The acid content is as high, the mix is so close, that I don't' see wasting time getting Zep's solution if you have KO to use locally? The KO used like Zep, in warm outdoor conditions looks like it will do every bit as well? There is another thread by Forum member Tfitz, who's just washed his boat totally inside and outside, which shows a white metal etch result using Zep.

But, the biggest difference it seems was Tfitz buffed 90% of the outside of his boat with power tools, so the various films were definitely removed before the acid etch. Tfitz also etched inside where he's in the process of bow-to-stern remodel, so again that is a different scope of project. His boat had much more advanced corrosion, there were places that had long term crevice corrosion under mounts, and fixtures on the hull; including a rubber rub rail at the sheer.

In these locations he attempted different levels of mechanical cleaning before etching. All that points to you using KO at a good strength, over cleaned-of-films surfaces, in warm conditions (and with FULL PPE!) should result in white metal cleaning.

cheers,
Kevin Morin
Kenai, AK

[bfetcho]

Thanks Kevin. I think I'll wait a few days and see what Hewescraft says and then I'll try acid etching again to see if that gets the rest of the corrosion. I would love to avoid the intense manual labor... If I do decide to go back to sanding, would you recommend a straight line sander? I sanded straight lines by hand with automotive wet/dry paper which doesn't look to bad. My concerns with a power sander is 1: Can I easily fine the grits that I need, 2: will the finish look swirled or bad? I would probably want to polish if I used a power sander I'm thinking.

Brett

[kmorin]

bfetcho, that's a good idea what if they come up with something that's not widely known?
In the meantime, power sanders as you know run or either AC or air and the actions get grouped by the power. Not many inline reciprocating (long board or jitterbug) type electric sanders, countless models from a dozen or more companies in pneumatic driven versions of inline reciprocating sanders. So if you can go air, you're able to afford very cheap and easy to find paper for... inline sanders and if you're confined to electric then the actions are more rotary, belt (kind of rotary) or random orbital.

Seems if you want to get some long-wise patterns in your power sanding then you'll probably have to run an electric belt sander (?) and the grits are available to super fine polishing belts (3M blue) so there's probably a path to grit graduation with that tool?

On the other hand if the grit is fine enough then a random orbital, smaller, cheaper, easier to handle will allow you to power sand and end up with a very fine grit of finish. The lines will be more visible in the coarser grits but like finishing dead plants for furniture, if the grit gets small enough neither the eye or the hand can detect them.

Looks are your call, pure rotary finish if the grit is polish level paste, will result in a shiny chrome surface so no swirl, on the other end of the grit spectrum if you stop with 40 grit the rotary sander's pattern will be pretty glaring.

Cheers,
Kevin Morin
Kenai AK

[Chaps]

I just did the bottom on this Pacific 20. The owner restored the hull sides (which were pretty ugly) using simply coarse and medium scotchbrite pads mounted on a square headed palm sander then coated it with sharkhide. I think it came out nice.

[Leucadia]

Everyone,

Thank you. There is some great information here in this post. I am about at this stage of my project. After reading I have decided to keep on with the manual removal of coroded areas, another application of natural based cleaner, acid washing with Zep, then wash.

The other issue I have to address is paint removal. I tried Jasco today and manually scraping with some success, but not the desired end result, certainly not totaly removed. Moreover all paint should be removed before acid etching ? Paint is only on the outside but there is some visible signs of corrosion or flowering.

I am going see if there are some better reccomended paint remover, I hate to keep spending money on items that do not yield the best results.

Thanks again., good reading.

Any updates ?

[kmorin]

Leucadia,
a note about paint removers- there is the terrible, toxic, terrifically terrifying (using today's terms for professional grade chemicals) and then there's the puffy, fluffy, feel goodie, orange and mint types that you can use in the dishwasher; big difference in the levels of products and the difference is in performance on the job. Main marketing difference? toxicity- the best will kill you if not used correctly, but it does the best job.

So.. when you say:

I tried Jasco today and manually scraping with some success, but not the desired end result, certainly not totaly removed.

I'm not finding fault, just asking if you're using the "professional ONLY" grades of stripper? IF you are, then to enhance its work #1 heat the hull, #2 warm the can of stripper (not hot mind you!!! ) # 3 do it more than once, and #4 don't spread is much at all.

If the full strength pro, toxic, Jasco is swabbed on, not spread, and if it doesn't lift the paint, do it again, warm it, and leave it a bit longer.

Stripped hulls are not sand blast clean, they have most of paint film gone and may need a couple of coats to get all the paint and then a good pressure wash, hopefully with some silica (soft sand) and while the stripper is still not hardened up.

Chaps knows 10times what I do about this and is the best resource so hopefully he'll step in to guide you?

The term 'best results' is very much relative!!! I'd say you're still going to need some surface treatment to get the hull stripped 100% to bare metal. Stripper softens, loosens, dissolves paint films but depending on the paint prep- blasting for example- you may need to plan to buff the hull to 'erase' the original anchor pattern depth of excavation to come out with totally clean surface?

Cheers,
Kevin Morin
Kenai, AK

[Tfitz]

I had pretty good luck removing paint off my boat with Aircraft Paint Remover made by POR 15. You can buy it at NAPA or auto paint stores. It took me 9 gallons to strip this boat and I wouldn't wish that job on my worst enemy.

[cboss]

The best looking chemical wash I have seen, is on Kiwi Ali boats AMF


http://bit.ly/1RfNfMy

[kmorin]

cboss, agreed some of the pictures show a total white metal etch, not to speak of some incredibly elegant designs, fantastic workmanship and overall clearly a world leader in quality welded aluminum (aluminium) boats.

Cheers,
Kevin Morin
Kenai, AK

[cboss]

Re Mill scale: I am surprised that caustic is not used to strip mill scale followed by acid to neutralist it.

[bfetcho]

After my first sanding project, I noticed that the flowering was coming back everywhere after several months. I'm back at it with power tools going to a courser grit to start (60 grit). I did a test patch to see where I'm at so these are pictures of sanding up to 600 and then a polish to see the surface better. It looks like I'v got the flowering but there are still a few depressions that I'm not quite sure about. Do I need to sand deeper?

Might have to zoom in on the pics to see what I'm talking about.

[kmorin]

Brett, I've generally etched with concentrated Zep, rinsed and left the metal go. So, all of my remarks should be taken with lots of salt- I've only polished one boat to that level and then etched after all polishing so... I'm in uncharted waters replying.

First, I'm not sure if this surface was coated? Nyalac? Shark Hide? or any other film after the cleaning? I'd say those products could act to trap a film of vapor inside, depending on application details and that could fire up the corrosion?

Next, in any polishing operation there is a sort of film possible, which why I'd etch after all mechanical surface treatments myself, and that might be from a 'worked' film of materials associated with the buffer and the surface of the metal. Pure Speculation on my part.. but I've buffed many surfaces and then wiped them with acetone and a clean white rag came away black for three or four wipings; leaving me to conclude there was some film on the metal?

You mention polish? was that a polishing grit buffer/sander or a polishing compound? What's in the compound- if there was one?

Last I have expressed my understanding of the mill scale problem in general terms and will try to 'zoom in' a bit. The film is thin, so is aluminum oxide only a mil or two (maybe three of four) so this film may not be removed if... the pits were already below this film's surface so they were 5-8mils deep? Your mechanical buffing/sanding/cleaning removed the top 3mils but left the pits bottoms?

The reason with may be possible is the original grits may not have been coarse enough to remove a full 10mils and get to base metal? Don't know, can't say and without some pretty impressive surface roughness measuring equipment, we won't know. What you can say is that if the pits' bottom 1/2 depth (even a few mils) was not removed or sanded off the metal's surface then leaving them may have allowed the corrosion sites to reform?

Also, if you didn't use a 'hot' acid, meaning concentrated solution, and I prefer to warm the boat and the acid with warm water in dilution- then the solution may not have been sufficient to lift the entire film within the bottom of any pits (regardless how shallow) and therefore all the pit sites could fire up again?

I was not there, and I'm not finding fault, I'm speculating based on what you've said (and my recall of the thread- not reread) and then simply asking: "What would answer these conditions?"

Not sure if raising lots of 'what ifs' is helping, but that's my reply to the various images you've posted.

Cheers,
Kevin Morin
Kenai, AK

[bfetcho]

Thank you for the response Kevin.

After looking at the photos I posted (after the post) it's pretty hard to see what I'm talking about. I guess I'm understanding that I need to be a little more aggressive with the sanding in these areas, maybe use a belt sanding instead of the orbital with 60 grit that I've been using. Being new to aluminum boats, I'm probably nervous to be too aggressive. I don't want to reduce the hull to 1/16".

As far as the hull is concerned, I have used 5+ gallons of pure concentrated acid (same acids and acid percentages as Zep A lume) along with hand sanding starting at 400 going up to 1500. This was my first round. My second round just started a few days ago and that started with an acid etch to the hull (also did the bilge for the first time) with the same concentrated acid. Next was mechanical sanding starting with 60 grit on a random orbital sander and also tried with a sheet sander at 60 grit. I have not gotten any further except for the test area that I posted pictures of. The only reason I used an aluminum polishing compound after I sanded up to 600 grit was to shine it a bit so any pits would show up. Maybe that thinking is wrong? I did not see any flowering but there are a few very small pits. It seems that if I try to sand to the bottom of some of these pits, I'm going to have some extremely thin metal. Granted these pits are the size of the tip of a ball point pen or smaller.

The plan is to finish with the 60 grit, maybe get a belt sander to remove a little more material and then work my way up to 1000 or so. I would like to etch after this (since I like this look) and leave it.

Yes, maybe it was too cold outside to be etching the bilge this time of year (it was a 60 degree day). It did foam up really well and turn white...maybe I should do it again in warmer conditions?


Note: I went to a local custom aluminum boat builder for a chat about a different project and he saw the "flowering" so we talked about this a little. He says "That's just the aluminum oxidizing." Great, thanks guy.

[kmorin]

brett, I'd keep whatever sanding tool or whatever grit flat to the surface and try to clean a uniform film of material, I see no reason in anyway to acid etch until the end.

I'd say that starting at 400 meant you left most of what pits bottoms were in a few mils intact? Surprised the etch didn't evict them however, if the polishing film were not off when you etched? I'm not sure there was any acid etching happening? I'd skip and polishing compound unless you have a known solvent for that compound- even if it were hot soap and water?

I'd say 60 was more coarse than needed and will make some serious work in the 80 and 100-120 range if you're headed for 1000!!! (?) I'd start with 100 and see if that will cut the pits. Use bright work lite at the surface and see if anything but 100 scratches show up? If needed drop to 80 but 60 is the only thing you've mentioned that could gouge the hull! AND IT COULD.

Save all acid until all sanded, all grits, washed and rinsed of soap warmed up and or hot, then do all at one time, no use to begin with acid as you're sanding off any gains of the etch.

Problem with the remark about oxidizing is that aluminum oxide is a thin film and the same 'color' of the base metal. Not white spots!

Cheers,
Kevin Morin
Kenai, AK