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mattttty
13-05-2012, 09:24 AM
Hey just got a new 4.3 m tinnie and it the process of fitting it out with rod holders ect just wondering if sikaflex 291 will prevent corrosion on self tapping stainless screws and on the holes i drill with a hole saw for the rod holders cheers

Moonlighter
13-05-2012, 12:17 PM
Nope, it might help a bit, but the better choice would be Duralac on the screws, that's what I use and have done for 20 years or more.

Cheers

ML

Seahorse
13-05-2012, 05:45 PM
I use tefgel. Get it from northside marine. In a syringe.

bf90
13-05-2012, 07:24 PM
moonlighter is right on the moo laaa !!! duralac is the deal!! On my tinnie I used dulalac on all screws, I pulled every screw and rivit out from factory fit out and put them back with duralac, holes ect for rod holders ect duralac screws and cutout I put sika on underside of what ever you are fitting and you will never have corrosion. I missed one bolt and the fuel filler on the gunnel and both have the corrosion. Cheers Brad.

Mr__Bean
13-05-2012, 07:26 PM
I fitted out my plate aluminium boat about 7 years ago now.

Items installed with Duralec smothered in the hole and on the screws - now corroded.

Items installed with Sikaflex smothered in the holes and on the screws - now corroded.

Items installed on nylon washers, with screws smothered in Duralec - now corroded.

Items installed on a bed of wet Sikaflex (both surfaces buttered with Sikaflex, screws wet with Sikaflex), cleaned up with a turps rag to leave a neat fillet. NOT CORRODED.

Stop the salt getting into the screw / screw hole and you have it beaten. Once it gets in it will find a void and corrode. Don't forget to get behind and completely cover the nut with Sikaflex too. Sure it is a lot of work, but so was the work to pay for your pride and joy in the first place.

- Darren

fishing111
13-05-2012, 08:13 PM
Agree with MB, have used Duralac everywhere and still get the paint bubbles. Just nature of the beast i think.

chris69
13-05-2012, 08:26 PM
The thing with duralac once applyed it need to dry i think before installing and better with bolts than scews,even the best prepaired surface is still no match with salt water and ally,steel stainless,a good wash when yo get home just prolongs the inevitable.

Fed
13-05-2012, 09:06 PM
Stainless self tappers would be my last choice for fasteners.

nigelr
14-05-2012, 06:42 AM
Stainless self tappers would be my last choice for fasteners.

What do you prefer to use, Fed?

Fed
14-05-2012, 07:47 AM
Drill the holes, repaint the exposed surfaces then use rivets & Duralac.
Had a mate with additional alloy rod holders riveted into his quintrex, never washed it and zero corrosion.

SunnyCoastMark
14-05-2012, 10:53 AM
I fitted out my plate aluminium boat about 7 years ago now.

Items installed with Duralec smothered in the hole and on the screws - now corroded.

Items installed with Sikaflex smothered in the holes and on the screws - now corroded.

Items installed on nylon washers, with screws smothered in Duralec - now corroded.

Items installed on a bed of wet Sikaflex (both surfaces buttered with Sikaflex, screws wet with Sikaflex), cleaned up with a turps rag to leave a neat fillet. NOT CORRODED.

Stop the salt getting into the screw / screw hole and you have it beaten. Once it gets in it will find a void and corrode. Don't forget to get behind and completely cover the nut with Sikaflex too. Sure it is a lot of work, but so was the work to pay for your pride and joy in the first place.

- Darren

Hey Darren,
What type of Sikaflex was that? - I have to fit out my beast shortly - so would be helpful - thanks.

Mark

Mr__Bean
14-05-2012, 03:13 PM
I can't remember, too far back.

But I reckon probably this stuff: https://whitworths.com.au/main_itemdetail.asp?cat=174&item=63842&intAbsolutePage=1&LinkedItem=63834&search123=sikaflex

- Darren

Greg P
14-05-2012, 03:56 PM
If you can weld them - weld them. Bolting anything other than nylon screws will eventually go down that path - nature of the beast.

TheRealAndy
14-05-2012, 05:31 PM
Been using duralac all my life on yacht masts, never had any corrosion problem. However, I did hear somewhere that one large brisbane yacht rigger has stop using duralac in favour of some other product do to failures. I just wish I could remember why and what it was.

PADDLES
14-05-2012, 07:40 PM
isn't the whole idea to simply keep salt water (electrolyte) out of the junction between the dissimilar metals? that's why mr bean's spooge it up with sikaflex method works, it seals it all up and no water can get in so no galvanic cell can be created.

TheRealAndy
14-05-2012, 09:55 PM
isn't the whole idea to simply keep salt water (electrolyte) out of the junction between the dissimilar metals? that's why mr bean's spooge it up with sikaflex method works, it seals it all up and no water can get in so no galvanic cell can be created.

Almost, the idea is to keep the two metals electrically isolated. Keeping the electrolyte out of the equation is a good start!

Mr__Bean
14-05-2012, 10:17 PM
It is not a good start, it is the key to success.

Darren

jahunt
18-07-2013, 01:37 PM
Old thread I know but Galvanic Corrosion (http://www.anzor.com.au/blog/galvanic-corrosion-keep-those-metals-apart/) is always a problem with Ali and Stainless (and Carbon). Isolating the dissimilar metals like Ali and Stainless is essential. Duralac does the trick but it goes dry and hard. I reckon Tef gel (http://www.anzor.com.au/chemical-products/lubricants-and-corrosion-inhibitors/tef-gel/product) is better and it also lubricates threads really well. Anzor Fasteners (http://www.anzor.com.au) in Acacia Ridge does it.

jahunt
18-07-2013, 01:42 PM
I know a lot of mast makers and that is what they are using on the big Carbon and also Aluminium rigs.

Fed
18-07-2013, 02:09 PM
A Spam Sleeper Cell, now I've seen everything.

Shark Poker
18-07-2013, 04:33 PM
The first thing is to look for any options rather than Stainless Steel (SST) screws or bolts.
Alum rivets or in some cases adhesive sealants are better for corrosion protection.

I use Lanotec Grease (Lanolin).
Advantages over Duralac include that it is very easy to clean up and does not leave the yellow stains., so put plenty on.
It is also non-drying, so can seal and protect a surface similar to an oil spill.
Also acts as a grease, making future removal of nuts and bolts or screws much easier.

I have discussed the choice between Duralac and Lanolin with different contractors many times, and you will get builders that swear by Duralac.
My opinion is plenty of Lanotec is better than little or no Duralac.
And plenty of Lanotec is better than none of anything, which is by far the most common method.

Further, I use nylon washers in between the alum boat and the sst washers, and sometimes foam tape as a gasket.

Pauly

Shark Poker
18-07-2013, 04:40 PM
Oh and if anyone would like more info re the grease, foam tapes, sealants, nylon washers and different fasteners that I use, or want to come around and play with some, just ask.
Pauly

ngc1955
21-08-2013, 06:40 PM
does anyone have serious corrosion in relative new plate alloy boats???

WalrusLike
21-08-2013, 08:33 PM
Stainless bow rails with a stainless thread in fibreglass.

I tried a stainless nut but it must have been an alloy nickle or something.... badly corroded.

I was thinking of stainless nyloc. Stainless nut without a identical locking nut just keeps loosening.


(Using Tapatalk on iPhone so can't easily 'thank' or 'like')

weeman
22-08-2013, 01:00 PM
Lanolin grease for me and no corrosion.

wirlybird
22-08-2013, 02:17 PM
http://www.probolt-australia.com/aluminium/aluminium-bolts-and-washers-countersunk/aluminium-countersunk-bolts-m4-x-0-7mm-x-15mm-pk-x-10-gold.html

Taa Daaa problem solved

fishing111
23-08-2013, 01:08 PM
How would Quicksilver 2-4-C with Teflon go on bolts or screws? Heaps cheaper.

Tef-Gel uses 40% Polytetrafluoroethylene, PTFE aka Teflon.

Can't find how much is in Quicksiver 2-4-C.

Malcolm W
23-08-2013, 01:38 PM
does anyone have serious corrosion in relative new plate alloy boats???


Not serious, but everywhere I have drilled into the painted surface, even with a rubber grommet placed in the hole there is corrosion. I have used duralac and sikaflex and its better than using nothing, but it wont stop the paint from bubbling.

Not so on the unpainted canopy, even where stainless meets ali with no sikaflex or duralac there is very little. It sems like paint allows salt to grow and corrode under it.