corrosion in aluminum mast - options - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #1  
Old 12-08-2011
Junior Member
 
Join Date: Oct 2010
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
samgary is on a distinguished road
corrosion in aluminum mast - options

I have recently un-stepped my mast in order to make a repair. Upon further inspection i have noticed a small area of galvanic corrosion above the cabin, on the forward side of the mast, where a stainless fitting was mounted. The corrosion has eaten a small hole, less than 1/4" in diameter through the mast The mast is keel stepped. The rest of the mast is in very good condition, with a minimal amount of corrosion.

My plan is to make a 4"x4" aluminum "band-aid" and rivet it on for reinforcement. I also plan on applying something to stop the existing corrosion as well as re-bedding all current fittings with tef-gel.

Any feedback/advice on process and or products would be greatly appreciated.
Reply With Quote Share with Facebook
  #2  
Old 12-08-2011
hellosailor's Avatar
Plausible Deniability
 
Join Date: Apr 2006
Posts: 10,447
Thanks: 1
Thanked 76 Times in 74 Posts
Rep Power: 10
hellosailor has a spectacular aura about hellosailor has a spectacular aura about
Sam, I would wonder whether the four rivet holes were going to cause more problems than simply cleaning up the 1/4" hole you have and then leaving it be. Perhaps just reinstalling the stainless with proper galvanic protection, as it was.
Reply With Quote Share with Facebook
  #3  
Old 12-08-2011
pdqaltair's Avatar
Senior Member
 
Join Date: Nov 2008
Location: Deale, MD
Posts: 2,107
Thanks: 1
Thanked 24 Times in 24 Posts
Rep Power: 6
pdqaltair is on a distinguished road
I would consider ultrasound inspection

The trouble is, you don't know how far the thinning extgends. A 1/4-inch hole may not be important at all, or there could be a large thin area. Ultrasound can also tell if the inside is smooth or rough. Of course, I do UT inspections and so this is free for me.

I would also be very surprised if the bandaid carried any important amount of load; compare the amount of missing area to the cross section of the rivets; it would take a LOT of rivets, close tolerance on the holes so that they carried load at the same time the mast began to deflect, and require a lot of drilling. Just a little slop under load, and the mast will begin to tear before patch loads up.

Is it a high load spot, and is it in compression or tension? Most masts fail by buckling up near the spreaders, not at the deck. A small hole at the deck in compression is probably unimportant.
__________________
(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")

"Well, I just climb up to them."

by Joe Brown, English rock climber




To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #4  
Old 12-08-2011
kd3pc's Avatar
Senior Member
 
Join Date: Oct 2006
Location: Callao, VA
Posts: 1,329
Thanks: 0
Thanked 8 Times in 8 Posts
Rep Power: 8
kd3pc is on a distinguished road
If any repair is made, I would opt for a sleeve and welding, by a metals familiar welder. The added rivets and needed drilling in the 4"x4" area(small), may actually weaken the mentioned 1/4" hole area.

Ultrasound of the entire extrusion is the best way to actually know what is going on...anything else is a guess or speculation at best.

If not, you may want to purchase an inexpensive bore camera and see what is going on inside.
Reply With Quote Share with Facebook
  #5  
Old 12-08-2011
Senior Member
 
Join Date: Sep 2011
Posts: 125
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 3
INMA is on a distinguished road
I had a similar issue, a rigger replaced the stainless fitting with an aluminium pad and aluminium fitting welded so that the weaker area was straddled and there was less chance of galvanic corrosion.

On another mast I noted a sleave welded over a weakened section.

In both cases the rigger avoided more holes and rivets.

If I was stuck away from a competent yard, then a rivetted patch would be an option but it would be replaced with a welded solution once I reached a suitable yard.
Reply With Quote Share with Facebook
  #6  
Old 12-09-2011
Junior Member
 
Join Date: Oct 2010
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
samgary is on a distinguished road
Thanks for all of the feedback!
After thinking about it more, most of the load is compression, as it is only 6 inches above the cabin. If anything, i think welding a patch would be the better solution, or applying some epoxy based paint to prevent further corrosion and keep an eye on it.

Thanks again for the feedback
Reply With Quote Share with Facebook
Reply

Tags
aluminum , corrosion , galvanic , mast , repair


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Crack in aluminum mast : options? samgary Gear & Maintenance 13 11-22-2011 07:33 PM
Preventing corrosion in mast lights? TakeFive Gear & Maintenance 9 03-07-2011 06:29 PM
Keel Stepped Mast corrosion question. travistowle Gear & Maintenance 7 08-21-2008 09:25 AM
Mast Corrosion? greencaptn Gear & Maintenance 3 07-09-2007 04:11 PM
Mast Corrosion Repair oldguyflier Gear & Maintenance 5 04-15-2007 11:06 PM


All times are GMT -4. The time now is 08:53 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.