How to remove unknown surface imperfections from boat

General boating discussion
Moj
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How to remove unknown surface imperfections from boat

#1

Post by Moj » Sun May 05, 2019 6:14 pm

I have a welded aluminum boat. I bought it used and it is unpainted. About 10 years old

There are surface imperfections on every uncovered surface of the boat. I have tried a number of products (including Nev-R-Dull, Salt-Off and Aluma Brite) to get it off but without success. I haven't tried abrasives or lots of elbow grease with the above products. Mostly just spray on and let them do their thing.

Has anyone experienced this before? Any suggestions as to what to do?

EDIT -- Changed the subject from "salt deposits" to "unknown surface imperfections" to avoid confusing people based on Kevin's comments below.
Last edited by Moj on Wed May 08, 2019 9:21 pm, edited 1 time in total.

Moj
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Re: How to remove Salt Deposits from boat.

#2

Post by Moj » Sun May 05, 2019 6:14 pm

Picture 1
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Moj
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Re: How to remove Salt Deposits from boat.

#3

Post by Moj » Sun May 05, 2019 6:15 pm

Picture 2
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Moj
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Re: How to remove Salt Deposits from boat.

#4

Post by Moj » Sun May 05, 2019 6:16 pm

Picture 3
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kmorin
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Re: How to remove Salt Deposits from boat.

#5

Post by kmorin » Sun May 05, 2019 10:23 pm

Moj,
not sure if that is really salt deposits? 98% of all welded boats have the mill scale left on the metal- it seems to appeal to their ignorant/uninformed/uneducated buyers???

#1 The shiny stuff ( a coating) is not aluminum.

#2 The shiny stuff is Mill Scale.

#3 The mill scale is porous and holds water vapor.

#4 Mill Scale actually has a galvanic potential to the underlying aluminum!!

#5 acid etching will help.

Zep-a-Lume is strong enough to remove mill scale, and would likely clean up your boat... and Zep is a Royal Pain in the stern to apply, handle and a clean up.

Buttttt: I'd suggest you find some Zep-A-Lume and apply it (warm) to a small area of the problems, using double gloves, and FULL PPE!! and rub it on with Scotchbrite (tm) pads.... Then rinse for a long time and see what your boat might look like if it were properly etched?

I also suggest you use the Archive/Search feature here to do a bit more exploration on your exact question??

Cheers,
Kevin Morin
Kenai, AK

The AAB.com Forum mill scale "gnat-zee"!!
kmorin

Moj
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Re: How to remove Salt Deposits from boat.

#6

Post by Moj » Mon May 06, 2019 7:27 am

Thank you very much for the reply. I had discounted mill scale because I thought I had read in other posts that Pacific Boats (this is a v2600) don't have that problem.

If that's not right I'll order the zep a lume and try it when the weather warms up to take your advice about the heat.

Best regards.

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Re: How to remove Salt Deposits from boat.

#7

Post by kmorin » Mon May 06, 2019 1:15 pm

moj, maybe this isn't as much a mill scale problem as it is a coating that was sprayed on? and now the coating has been penetrated and is showing the corrosion under the film? Another Pacific owner had Nyalac sprayed on his... and he removed it by washing with acid and rubbing with Scotchbrite (tm) then I think he recoated with "shark hide"? don't recall the brand name.

Rubbing on it with 3M Scotchbrite (tm) will sure tell a lot about the problem. May have to use a power tool if the coating (?) is still in tact? otherwise it looks like mill scale corrosion.

cheers,
Kevin Morin
Kenai, AK
kmorin

Moj
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Re: How to remove Salt Deposits from boat.

#8

Post by Moj » Wed May 08, 2019 6:52 pm

Thank you for the suggestion. I went out and bought some Scotchbrite pads. Long story short, the imperfections came right off. Image below.

Left: Control

Middle: Scotchbrite Maroon General Purpose Pad

Right: Scotchbrite Pad + Strong acid aluminum cleaner

Does this mean that it is likely mill scale?
Attachments
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kmorin
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Re: How to remove unknown surface imperfections from boat

#9

Post by kmorin » Wed May 08, 2019 10:11 pm

Moj, yeah pretty much. The item that throws me the most is the color in the photos... that blue lacing or spider webbing makes me think some other factor is at work?

But as long a you can wipe/rub/abrade the surface and etch it too... and it comes clean- well I guess you have your work cut out for you?

Cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: How to remove unknown surface imperfections from boat

#10

Post by Challenge » Thu May 09, 2019 10:22 am

So Kevin now that he has cleaned the surface will the mill scale come back on the middle rod holder? the one not treated with acid?

Thanks

Rick

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Re: How to remove unknown surface imperfections from boat

#11

Post by kmorin » Thu May 09, 2019 12:10 pm

Rick,
in general if the mill scale is left on (?) or if there is corrosion due to clear coats or anodizing that has been permeated the corrosion method is due to the film. Mill scale usually not seen on extrusions - like pipe or angle is porous and hold water vapor allowing the moisture to create an acidic corrosion site.

Usually corrosion from mill scale and is a whitish chalky (when dried) deposit as the metal has been converted to an oxide and salt composition from the original alloy.

Nyalac (sp?) Shark hide and others are just clear lacquers/paints/finishes that act to keep a film tight to the metal and therefore in the as left visual finish level. When the paints are penetrated a similar event happens; the underlying metal begins to give up its oxide layer molecules to the (now) acidic water and a similar corrosion begins.

Once the films are all lifted and the metal allowed to "breath freely" there is no source of corrosion any longer. If water is allowed to stagnate while trapped in a thin film- that is when the condition comes about. If you look at Chaps' avatar there is a work boat that is pretty much 'bare metal' and that is the best condition.

However, due to Skipper preference for paints, clear coats, vinyl hull panels and so on.... covering film induced corrosion is a major factor in a 2-20 year old welded aluminum boat. Work boats tend to be less concerned with surface finish and they are often acid etched - rinsed and left to the elements.

If the surfaces are stripped of all paints, clear coats, and etched (or simply buffed with Scotchbrite (tm)) and films are all removed the metal should remain uniform in color (except near the waterline) and have no white flowers or other corrosion sites.
Paint Corrosion.jpg
Paint Corrosion.jpg (61.34 KiB) Viewed 172 times
Here is an image that I hope helps? The blue is a painted topsides panel and the lower part of this hull is not painted. But... there is similar corrosion in both panels. First the upper panel, under the blue, appears to have sun protected but not acid etched mill scale in tact? Then paint (not sure kind or sequence) doesn't appear to have adhered all that well, and the water trapped under that created this white pitted area.... and then the paint lifted in this region.

However, the rest of the panel below the painted strip shows plenty of miniature pits beginning, this builder did not acid wash his boats to the best of my knowledge? So the tiny white 'flowers' is the type of visual indication of corrosion associated with intact mill scale open to the weather. Some of the streaking seems to indicate there was some acid washing ?? but the continued corrosion shows that some film was left? Not clear on my part as I was called to the boat for more serious reasons and only walked around and took this pic to show what we've talked about so many times.

The original mill scale protected (for a while) by the paint is intact and looks like the fresh sheets' surface... But if the paint is breached or (as below) the mill scale is left on without removal this is a typical surface appearance result.

Hope this is enough answer?

Cheers,
Kevin Morin
Kenai, AK
kmorin

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