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Old 04-10-2010, 08:11   #1
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Aluminum Toe Rail Cancer ?

Wondering what lies ahead when you see this type of pitting and corrosion on the toe rails ? How best to slow it down ? I plan to put a bead of caulk to stop the moisture intrusion which iToe Rail Aluminum Corrosion?s probably not helping !

Any of you seen this before ? How best to correct and slow it down ?
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Old 06-10-2010, 22:07   #2
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Corrosion may be as a result of contact between aluminium and steel. If your deck is steel, you need to provide a barrier in between the toe-rail and the steel deck. You may aslo need to provide a barrier between the toe rail and the fastening bolts.

You can eiterh use a physical barrier like a gasket of some sort, or you can use a paint-type barrier like Duralac anti-corrosive jointing compound (or equivalent). For the bolts again, you can use Duralac, or some types of toe-rail are suitable for a bolt insulator

The one below works well for our toe-rail with countersunk 1/4" bolts.

Ronstan Series 32 T-Track Track Bolt Insulator: Mauri Pro Sailing
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Old 07-10-2010, 06:11   #3
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if thats asteel deck then theres the problem, its looks like a replacement job. As to Duralac, thats fine for screw and bolts but not suitable for long strips (a) it will cost a fortune and mail order duralac is regarded as a hazardous substance. Best use a physical barrier, HD poly plastic of some sort.

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Old 07-10-2010, 07:05   #4
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Originally Posted by Weyalan View Post
Corrosion may be as a result of contact between aluminium and steel. If your deck is steel, you need to provide a barrier in between the toe-rail and the steel deck. You may aslo need to provide a barrier between the toe rail and the fastening bolts ...
Indeed.

Bimetallic corrosion can only be prevented by Isolation:
- isolating the metals electrically using insulators
- isolating the metals from the environment using a coating
- choosing metals that are close together in the table, or coating one of them to achieve this.

Dealing with a fibreglass boat (Cal 48), here’s an excellent article taken from Good Old Boat magazine:
A NEW TOERAIL FOR AN OLD WARHORSE
Good Old Boat - A new toerail for an old warhorse article
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Old 07-10-2010, 07:54   #5
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I had similar on a GRP boat.... turned out it was being caused by electrolysis... the wire to the bow nav lights had been exposed and was touching metal... someone had dragged down on me and I figure the knock which bent it back slightly did the damage..
Check for that with a tester first before pulling things apart
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Old 13-11-2010, 13:08   #6
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Originally Posted by dadidoc View Post
Any of you seen this before ? How best to correct and slow it down ?
Very interesting - this week I surveyed a 41' Morgan with two similar holes in the toe rail. I remembered your post and find it curious that your boat is also a 41' Morgan. I noticed that each hole is directly in an area of stress. My first picture shows wear in the toe rail perforation, and given the location it is likely from a block being shackled to the toe rail. The second picture has quite a few gouges in the rub rail directly below, and inside there is a bulkhead at that location and its tabbing is cracked from above the rub rail to the hull-to-deck joint where the toe rail is bolted through.

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Are the holes in your toe rail in areas that have been stressed?

I am currently working towards my ABYC Marine Corrosion Certification - hopefully in the next few months I will have an answer for your second question.
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Old 18-12-2010, 06:46   #7
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They are not in an area of stress - pretty much aft of where the jib sheet snatch block attaches. Thank for the postings - keep it coming - looks like I may have to find a replacement toe rail
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Old 18-12-2010, 08:11   #8
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Originally Posted by dadidoc View Post
Wondering what lies ahead when you see this type of pitting and corrosion on the toe rails ? How best to slow it down ? I plan to put a bead of caulk to stop the moisture intrusion which iToe Rail Aluminum Corrosion?s probably not helping !

Any of you seen this before ? How best to correct and slow it down ?

What do you use to clean you decks with? Both low and high pH cleaners will corrode Alum. A nick etc in the metal will provide a place for the cleaner to concentrate. Chlorides in seawater will also accelerate corrosion and if it is getting to collect in a hole/nick you are going to get faster corrosion there in the form of a pit.

I doubt that putting the caulk down is going to solve anything for the a pitting corrosion. Where is probably is a general corrosion problem under the rail. The caulk could even make it worst as it is unlikely it will be total and once water etc gets under the area you are going to get an under-deposit corrosion issue faster than the current one.

I would look at using an Alum cleaner/passivator to clean the metal and provide a protective film back on the metal. Now that you have the pits/corrosion you basically need to seal them. You need to get this down under the rail and flush it very well afterwards.

As others have said; yes an electrical problem would cause lots of corrosion. But normally it's going to be at location of current in/out and not at a random section of the rail. So I doubt this is the problem.

In the end there probably is already a lose of surface protection under the rail that nothing short of removing and retreating/replacing is fully going to really solve.

PS - I make my living doing corrosion control and chemical treatment for it. If the "experts" want to tell me how wrong I am they are welcome, but I'm not going debate.
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Old 18-12-2010, 17:20   #9
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Those li'l scratches are nothing.
Here is 30 years of SS fasteners passing thru an aluminum toerail. It's all erosion. Had to cut the heads off the fasteners to get them out. The stuff that lurks beneath can surprise you.
Once it gets so far, replacement is the only cure.


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