Bow tang repair causing rust staining down hull?

Hi all,
a couple of years ago I repaired a bow tang on the port bow of my Nacra 5.2. It was loose and showing some cracking (probably from inwards directed load and years of neglect). I used epoxy and had the lids off so I could structurally re-seat the tang and rebuild the damaged layup. I know it is 100% sealed in and no water gets through there to the inside.

What puzzles me is that the repair side now has a clearly visible brown rust streak running down the hull while the unaltered side shows no staining at all.

Could there be a compatibility issue with the epoxy I used and the stainless tang? I can't think of anything else. The epoxy feels tough, it has hardened well and even supports a thick layer of (polyester!) gel-coat to this day.

Should I just clean it up periodically with some acid or is there a really good way to seal the rusty tang and keep it from rusting all over my boat?

Thanks in advance for any advice,
Dennis

Did you drill or Tap threads... add any new hardware or fasteners... weld? anything? Tools can leave bits of carbon and that rusts off the stainless. Just cosmetic though.

Hmmm. I did file and sand the tang quite aggressively to clean it up and to give the epoxy something to key into...

That could well be all there is to it!

I have the same experience. With all the stainless bolts and plates of my hulls. I've sanded everything also in the idea of cleaning and finding good connecting with the epoxy where necessary. Like you used to do between layers laminate and glueing things on and with epoxy.

Well, the rust gives the cat a sturdy used look.

Did you use any carbon fiber in your repair? It can cause stainless steel to rust.

Jake, I cannot answer for Dennis, but I used, besides glass and kevlar, at least 2 layers of carbon for my hull skin-laminate.
And on the places where bolts came through even double or triple. (My hulls are not hollow,but have a solid foamcore! So bolts are fixed and glued from inside)

So, your remark is spot on. I wondered already a few years ago where the rust came from. It looked like from inside, because painting it over with 2-C PU paint didn't help at all.

No, I didn't use any carbon in the repair, I'd be more worried if I did...
I kind of like the war-torn "Mad Max" look though, it suits my cat well and beats waxing and polishing every year. Oh the joys of an old boat. That and "screw the class-rules"!

Dennis

Here's a quick reference on the Galvanic Material Series. Carbon Fiber (Graphite) is at the very bottom.

http://www.corrosionpedia.com/2/140...ies-galvanic-compatibility-and-corrosion

Aha, its probably the platinum D shackles I fitted then... ;-)

I remember using graphite rods for an experiment in a science fair at school a long time ago. The teacher wouldn't give us platinum electrodes...

my next band will be named
"Galvanic Corrosion and the Sacrificial Anode"
or Gcatsa for short

Can't say that I'd have a huge comfort level seeing rust coming from a component responsible for keeping my mast upright. Just sayin...

Mike

Guess I'll just have to just clean it up and see whether there is any more staining or not. There isn't room to add more epoxy in there, maybe some WD40 though...
I'll also check to see if it isn't being caused by any of the shackles or other fittings I have attached there rusting due to them perhaps being made of dissimilar Stainless steel types. The staining might be coming from higher up and leaking down.

Not WD40... I think Lanocote

http://www.westmarine.com/buy/forespar--lanocote-corrosion-inhibitor--129975

To clean off rust: http://www.magicarustremover.com/

tef-gel is my product of choice