Preventing SS/Aluminum Corrosion ??

NorthRiverRick · 02-20-2005, 03:17 PM

Hi,

I'll be putting some new trim tabs on my aluminum boat. That means contact between SS and Aluminum with SS bolts to connect the two. This is my second aluminum boat so I know the result. I need to isolate the two as much as possible.

It has been mentioned here on one of the boards that there is a compound that can be used on the bolts to prevent the corrosion. I also remember someone recently mentioning a green paint-like stuff for the same purpose.

I've searched every which way and came up empty. Does anyone know what I'm looking for?

Keta, are you out there? You seem to be able to conjure up a multitude of answers for people...anything for this one?

Thanks for any help

Green Machine · 02-20-2005, 04:09 PM

How big are the bolts? For small things I use aluminum bolts and screws on the boat. I think you can get up to a 1/4 inch and still be plenty strong. Just an idea.....You may need something stronger.

Green Machine

ketch99901 · 02-20-2005, 07:01 PM

The compound you are looking for may be Tef-gel. It is nonhardening, intended to prevent crevice corrosion on SS fasteners used in aluminum. If you do a web search you'll hit the manufacturers site. A 1 oz tube from Fisheries Supply runs about $11. I just took delivery of a new boat, and thought I'd give it a try. Been busy backing out SS fasteners in the hull and coating them with Tef-gel. I'm going to try to isolate my new tabs from the hull with 3M Scotchwrap Corrosion Prevention tape. Its several mils thick, made for use between dissimilar metals. I've used it in construction between aluminum and galvanized steel with good results, thought I'd try it on a marine application. Its available from most marine suppliers or electrical suppliers. Hope this helps.
Dan

Beer Waggin · 02-21-2005, 04:42 PM

Rick, Rick, Rick... galvanic corrosion, it'll getcha every time.

Ketch has it right. Teff-Gel is what you want.
I have a tub of it and am reinstalling all of my rod holders wih it.

The cheapest place I found it on the web was at http://shop.goebms.com/pss/products.html

Or search Practical Sailing Solutions.

I couldn't find it locally, but I didn't look real hard.

Another thing to do is to isolate the SS bolts from the alum with a plastic washer.

NorthRiverRick · 02-21-2005, 06:21 PM

Thanks Dan and Dave,

I'll order some of that goop and try it. I looked all over the Portland area and almost everyone looked at me like I was smokin' somethin'

and this includes the marine stores

Gundog · 02-21-2005, 06:38 PM

I have used electrical corosion inhibitor in the past without a problem. I am not sure it is the right thing to use but it has worked for me.
Mike

02-21-2005, 07:02 PM

Best,
Completely isolate the SS from the aluminum with a thin piece of UHMW or some thing similar behind the tabs and isolate the bolts with buttons like these

Second Best,
De-Ox or NoCorode electrical corrosion inhibitor.

Flush Release · 02-21-2005, 07:15 PM

Monel bolts and De-Ox, if you can't get Monel use 316 SS and not 304 SS. Also put never seeze on the threads. I have used de-ox on aluminum that was imersed in the brine and it works fine. Bonding also may be a consideration.

Ketch99901, Do I know you? Lived in KTN from 85 thru 99 and worked on a lot of boats up there.

FourFun · 02-22-2005, 09:04 AM

I've been looking for this stuff locally also with no luck. However, I've been told that the non-corrode electrical stuff does the same thing, and that is easily found. I will be applying that this weekend on all the ss screws in my boat. Hope it does work.

NorthRiverRick · 02-22-2005, 03:35 PM

Thanks for all the replies. I knew you folks would come through for me

Regards,

SouthCoastStu · 02-22-2005, 04:45 PM

Keta-
Have you ever heard of or used a spray called ACF 50? I was told it was developed for the aircraft industry. Supposedly creates a corrosion blocking shield. I read good things about it and bought a can. Been spraying it on little problem areas (zinc coated steel), jury's still out. I'm wondering if it would do good on SS/Aluminum?

Flush Release · 02-22-2005, 08:35 PM

Stuff is good for about 6 months before you have to re do it. Dynol AV8 is a better inhibitor.

02-22-2005, 10:20 PM

Flush Release works in the aviation industry and knows non ferris metals, how they react and what to do to keep them from desolving in saltwater.

Gundog · 02-23-2005, 06:35 AM

Rick,
If you would like to try some of the electrical inhibitor I will bring you enough to last your life time to the next ACN class. The stuff I have looks like axle greese it takes very little to do the job. Send me a PM.
Mike

USCGBoating · 02-23-2005, 01:39 PM

You put a few coasties to work on a project and someone will come up with a cheap way to keep from having to do a lot of work. Me being one of them. We constantly had a proble with the aluminum wasting away around S/S bolts. If you look how the corrosion process works its main cause is from salt water infiltrating the nooks and crannies around the bolt and along the threads. Once it is trapped there in the dark it does its electrical majic.

We found several ways to prevent it. There are, as previously mentioned, nylon washers availble that you can use. Also we have used a S/S washer that has a neoprene coating on one side. (we use to get them from Eugene Fasteners) When we would put the hole mess together we would put a dab of silicone under the washers and on the bolt threads to keep the water from seeping in. Worked well and it reduced our problem by 90 pecent. We wiped away the residue and it looked clean.

ron m · 02-23-2005, 08:44 PM

More stuff I didn't know that raises questions. I have an aluminum boat, an EdWing. Do I have to worry about this reaction, actually preventing the reaction, everywhere on my boat or just the parts of it that get exposed to saltwater, including spray? or just the parts that are below water?

and thanks for bringing up the topic and for the info already given.
ron m

NorthRiverRick · 02-24-2005, 05:36 AM

ron,

You absolutely need to be concerned about this problem even if you just drive past the ocean with your boat in tow. I have great experience with the results on my last boat.

You can wash the boat all you want, but as USCG has stated, when the saltwater gets in around the threads or those areas of SS contacting your Aluminum it will corrode the AL.(and you can't wash/rinse the salt out of all those areas) It actually can take years for the process to create a true problem but you will see the beginning of the corrosion in a very short time.

Do all that you can with the solutions provided above to prevent the problem from starting.

Thanks for the info folks.

ron m · 02-24-2005, 07:19 PM

Thanks. I'm going looking for some of these items tomorrow. Hope to get them installed soon, but probably not before Sat's trip!
good info here, nothing like have someone else's experience to learn from
ron m