AluminumAlloyBoats.com

Greetings AAB,

I hope everyone is having a good spring. 

This picture from a recent outing, I like it as it makes the boat look big!  The undercarriage of the hard top shows mill scale flowering correct?   The topside was all ground uniformly and has a nice weathered grey.  The underside looks like the fabricator spot ground wherever he was welding and mill scale was never removed.  

Should I acid wash all these surfaces?  This top is about 10 years old Thank you!

Eric

TinCup
yes, that does look like flowering on un-etched surfaces and acid etching will sure knock down what's there and prevent it happening more deeply or causing damage.

Could be said of any part of a welded aluminum boat.  Spraying overhead isn't the most pleasant work- full oil skins and full PPE including splash googles and face shield if at all possible?  Just the slightest mist of Zep isn't good for any part of your carcass! 

Cheers,
Kevin Morin
Kenai, AK

OK thank you for the confirmation. It's such a small area, I think I'm gonna try applying by wiping it on with a sponge, cloth or similar, followed by a hose off.

How did it come out?

Haven't done it yet, been too busy fishing! Maybe this weekend I'll get to it.

Did run into Clambo yesterday at the ramp in Barrington. Also saw another Pacifc HT on the water (23' maybe) in the Mount Hope Bay area yesterday.

Finally got around to acid washing my top over the holiday weekend. I couldn't find Zep A Lume and used a product called Aluminex that I found in a local marine store. Was pretty easy and straightforward. Faceshield, mask gloves and full bunny suit. Applied the acid with a foam brush and wound up applying at full strength after 50% dilution with warm water didn't seem to have much of a result. It definitely etched the aluminum and the foam brush started to break down at the end.  Was a quick job; apply to an area, rinse and repeat.  More time was spent on prep.  

The surfaces that have the corrosion flowering are noticeably smoother, the flowering is still visible but hopefully now curtailed. I did get a little streaking but it's minimal and barely noticeable.

The lingering issue is this ring of (what I believe is) corrosion around the window gaskets.  See pictures.  The worst of it is on the exterior port side, first pic. Starboard and interior areas are much less severe.  The grinding pattern suggests to me that these areas were fully ground before the gaskets went in.  Not sure why the corrosion is happening and how to stop it. 

Threw in a bonus fish pic, why not.  I think this was the first striper of the year, most of them are much bigger!       
 
 
 
 
 
 

That corrosion around the windows is from the carbon black leaching out of the rubber window gaskets. Carbon black is electrically conductive and electrochemically very noble. The corrosion occurs as a result of the high nobility carbon in the rubber being in direct contact with the low nobility aluminum in the presence of salt water moisture which acts like the electrolyte in a battery.

This situation also occurs on aluminum boats fitted with black D rubber bumper strips bolted directly to the sides of the hull. The carbon in the rubber is as galvanically aggressive as applying copper bottom paint directly to a bare hull bottom. The higher nobility carbon in the rubber pulls electrons away from the aluminum atoms which is what causes the pitting/damage.  When aluminum atoms lose electrons the aluminum falls apart (pits) resulting in what you see above.
 
 
 
 
 

Chaps, thank you! Unfortunately that is not a great prognosis for me.  

So is the solution to re-gasket the windows with a different material?  Any recommendations on how to proceed?  

It's really more of a cosmetic issue, a fairly common situation. Your window openings aren't going to get eaten out. On the other hand, the way to make it stop would be to have the gaskets replaced with some made of white rubber or replace the windows with framed windows like those from Diamond Sea Glaze or others.
 

OK good to know. Thanks once again!