unsure about what causes this corrosion

[garyfdl]

Originally Posted by boatpoker

Common susceptibility to crevice corrosion and deoxygenation.

[Scubaseas]

Originally Posted by boatpoker

My copy does not say that. Can you provide the paragraph number or a screenshot of that.

I stand corrected. The only reference I can find in ABYC codes I have on my laptop here in Maine is to double clamping is for exhausts and fuel filler hoses. I'll take you word that double clamping of hoses below the water line is not an ABYC standard. It is a European standard from what Steve D'Antonio is telling me and probably just good practice if there is a proper nipple to support two clamps, I see the OP has some hose clamps (single or not) that would not pass ABYC standard as they don't look like all 300 or better stainless.

But you are 100% correct. Double clamping is not an ABYC standard except for exhaust and fuel filler hoses. My sincere apologies. Not a marine service provider. I am a former ABYC member though.

[Lrak]

Originally Posted by kapnd

Bronze is proper for seacock, never stainless.

Most modern seacocks are ball valves with bronze bodies and stainless stems and balls. Some will be bronze with chrome plated brass ball and stem. Others will be all Marelon construction. Very few builders use all bronze tapered plug seacocks these days.

My CD25 came with brass gate valves screwed directly onto the thruhull. That worked for 35 years. I'm not concerned after moving to Apollo bronze ball valves with stainless stems and balls screwed onto Groco bronze ball valve flanged adaptors that convert from straight to tapered threads. Cheap and easy to replace the valve bodies every 10 years and also carry wood or foam plugs and a spare ball valve in each size in the very unlikely event one of the internal stainless components fail.

[boatpoker]

Originally Posted by Scubaseas

It is a European standard from what Steve D'Antonio is telling me

Neither does that requirement appear in any of my RCD (Euro)standards and I've never seen a Euro production boat leave the factory that way.

[OneBoatman]

When bronze, an alloy composed mainly of Copper and Tin is exposed to oxygen it forms surface oxides which we call patina. The film is a surface phenomenon. it is normal, and not a cause for concern. The greenish film is made up of mostly cuprous oxide. This is neither a reason to purchase or not to purchase a particular boat. Yes, do familiarize yourself with all thru-hull fittings. Know what they serve, and make sure they operate freely and have proper backing plates.

[cyrano138]

I appreciate it everybody's input. I decided to pass on that boat. Most of it looked very seaworthy and well taken care of but for the price I was looking for something I could sail around for a season and not have to haul out right away and start messing with. By the time I got it hauled out and replaced three of the five I would have been looking at at least 2,000 bucks.



I am going to look at another Cape Dory tomorrow. Crossing my fingers!


I figured it was just patina but it did look more serious and crusty than I usually see on bronze fittings so I wondered if it might be accelerated or exacerbated by the grounds. I didn't even realize some of them weren't proper seacocks until somebody pointed it out.

[lestersails]

Originally Posted by cyrano138

I appreciate it everybody's input. I decided to pass on that boat. Most of it looked very seaworthy and well taken care of but for the price I was looking for something I could sail around for a season and not have to haul out right away and start messing with. By the time I got it hauled out and replaced three of the five I would have been looking at at least 2,000 bucks.

I figured it was just patina but it did look more serious and crusty than I usually see on bronze fittings so I wondered if it might be accelerated or exacerbated by the grounds. I didn't even realize some of them weren't proper seacocks until somebody pointed it out.

And the bigger concern was that some would not turn at all. Pretty dicey to sail a boat with seacocks that cannot be closed!

[GypsyOwner]

Originally Posted by garyfdl

I'm gong to pile on and agree with what has already been said. With the ball valves, you can replace them with stainless. Real seacocks would be better. The regular seacock(s) can be rebuilt.

The green is oxide from the copper in the bronze alloy.

There is also something about double hose clamps on through hulls; maybe another member can chime in on that?

Love that deep blue. The copper in that bronze gives you nice colours: black/red or a browny mixture for the oxides. Blue for sulphates, chlorides and hydroxides, Green for carbonates. As long as it’s a thin layer you can just brush it off. Watch out for bright pink copper under your corroded ‘bronze’ - it means your ‘bronze’ was brass (copper-zinc) and all the zinc has gone leaving a weak copper sponge that will break as soon as you turn it.

[Colonel Bob]

Originally Posted by kapnd

Bronze is proper for seacock, never stainless.
The rotten backing sound pretty important to me!

My suggestion is to ditch the thru-hulls and ball valves (and rotten wood backing plates) with Thru Design thru-hulls and valves with the AYBC approved collar. Prices are reasonable and quality is excellent. Peace of mind and no bonding issues.