Anti corrosive barrier
Printed From: Yachts and Yachting Online
Category: General
Forum Name: Repair & maintenance
Forum Discription: Questions & tips on the subject
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=5514
Printed Date: 15 May 25 at 3:23am
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: Anti corrosive barrier
Posted By: English Dave
Subject: Anti corrosive barrier
Date Posted: 13 May 09 at 5:05pm
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I need to squeeze a thin strip of stainless in between an existing stainless steel fitting and my aluminium mast. Normally I would throw on a load of Duralac and be done. However, I cannot fully remove the fitting so I will have slide the steel strip into place. This makes applying the Duralac (and keeping it on) more difficult. I have been told that if you chop up a 2litre milk bottle, the plastic will do just as well as the duralac. Certainly easier to slide in alongside the steel strip (it's a shroud plate but I'm not using it as this - it may appear in "Pimp" in a few weeks.) Purists may say stick to the Duralac but wonder if anyone else has experience of the milk bottle technique? ------------- English Dave http://www.ballyholme.com - Ballyholme Yacht Club (You'd think I'd be better at it by now) Hurricane 5.9 SX RS700 |
Replies:
Posted By: alstorer
Date Posted: 13 May 09 at 6:11pm
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hmm. It'll certainly stop a galvanic cell setting up when merely damp, but water will still get to both metal and surfaces, and when properly wet all the way around. The Durlac doesn't just act as a spacer keeping the two apart, but as a barrier coating helping stopping water getting in.
It'll kindof work, certainly better than the two pieces being in contact, but there's a chance you're still creating a location for hidden corosion. Do you want to take the risk or not? ------------- -_ Al |
Posted By: didlydon
Date Posted: 18 May 09 at 3:18pm
| So, excuse me for asking what might appear an obvious question - I'm not familiar with this. Do you apply this Duralac to anything stainless where it comes into contact with an ally mast or boom? Is it like a grease or mastic that goes between fittings like kicker straps & eyes for blocks & things, thus preventing an electrolytic reaction? |
Posted By: laser193713
Date Posted: 20 May 09 at 10:34am
You are breaking the most important rule here! ------------- |
Posted By: Alistair426
Date Posted: 21 May 09 at 4:24pm
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Didlydon, Duralac is a yellow paste which comes in a tube and gets everywhere when you use it...normally because I always seem to have to bolt fiddly things to masts. It's not just for stainless v ali contact; I was advised to use it when replacing fittings on a carbon mast as well. |
Posted By: JimC
Date Posted: 21 May 09 at 5:57pm
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I'd use duralac. By all means use your bit of plastic milk container to smear duralac into the gap though.
And yes, if anything its *more* important to use it on carbon spars than on aluminium. |
Posted By: didlydon
Date Posted: 21 May 09 at 10:25pm
Ah.... Cheers Alex. I understand now. Thanx for the reply.. I guess I should've used it when I fitted a new kicker eye to my mast.....
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Posted By: Granite
Date Posted: 22 May 09 at 2:54pm
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Duralac is zinc chromate paste and acts as a sacrificial anode. With Aluminium and stainless the ali corrodes. With Carbon and pretty much any metal the metal corodes. If the corrosion products cause the metal to expand then the carbon can get damaged, like putting an ali tube in a carbon mast (Old RS600 masts) You want to avoid getting it onto your skin as it is quite nasty, it is also a pain to wash out of clothes. ------------- If it doesn't break it's too heavy; if it does it wasn't built right |
Posted By: timeintheboat
Date Posted: 22 May 09 at 3:58pm
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A job for me later this summer then as I replaced all of the load bearing (and loose in some cases) rivets on one of ali masts with A2 stainless steel bolts. I've also discovered that apparently I should have used A4 stainless and not A2 (is there a big difference?) and err no Dualac. Does it survive exposure to the elements and the occasional dunking? ------------- Like some other things - sailing is more enjoyable when you do it with someone else |
Posted By: Alistair426
Date Posted: 22 May 09 at 6:04pm
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A2 stainless will survive in the short-term, provided you give it a sloosh down with fresh water on a fairly regular basis. You might start to get a bit of discolouration but that, in the, again, short-term, shouldn't present a problem. Looking at the state of a lot of the fastenings on several SMODs, it is clear that their suppliers are more than happy to use A2 rather than the significantly more expensive A4. But then again....there are different qualities of A4 stainless out there
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Posted By: English Dave
Date Posted: 23 May 09 at 10:06am
Point taken. Perhaps I should start a new "Bodge Club" thread. ------------- English Dave http://www.ballyholme.com - Ballyholme Yacht Club (You'd think I'd be better at it by now) Hurricane 5.9 SX RS700 |
Posted By: JimC
Date Posted: 23 May 09 at 2:51pm
Its not! I always though that, but the other day I looked it up and it is in fact Barium Chromate and it seems the chemistry going on is a lot more complicated. I didn't find a source I trusted to work out exactly how it works - especially with carbon - but it definitely says barium chromate on the tube I have. |
Posted By: Granite
Date Posted: 23 May 09 at 3:30pm
You are absolutely right, used to use it all the time at work and everyone either called it Zinc Chromate or Chicken Sh1t. Looking at the MSDS it is not as quite as nasty as was made out either. ------------- If it doesn't break it's too heavy; if it does it wasn't built right |
Posted By: didlydon
Date Posted: 23 May 09 at 8:21pm
Ok, Duralac it is then whenever I replace anything stainless on me ally mast! Thanx for the info.
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