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  #16 (permalink)  
Old 05-20-2005, 05:32 AM
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now its been a few years but when i used to work for the yacht co. i worked closely off and on with one of the corrosion engineers. all the running gear and metal on the boats were connected together. reason for this was each type of metal has a different electrical potential when in salt water. when connected together the potential becomes equal and highly reduces the corrosion. it basically allows the electrical current to run through the bonding wire rather than the water destroying the struts, rudders, etc. this is why i recommend a small connection between the two. now another thing, we are talking about salt air here not letting the car sit in salt water for a month. i really think you'll be fine if you put a couple coats of epoxy on the body and pans then glue them in. just make sure the aluminum is sealed really well. that will be the one to corrode. make sure you round over any sharp corners since paint doesn't stick to a point very well. any break in the integrity of the epoxy or paint will be somewhere for the air to begin blistering the paint

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Old 05-20-2005, 05:38 AM
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alum

My outboard boat motor is all alluminum and it has a sacrificial
"anode" that is a piece of some kind of metal only a couple of
square inches in size bolted directly to the housing.
It's not in any kind of path for electricty. I don't know
how it works but from what I understand all outboards have
one of these for the corrosion problem.
I sure wish I could use this system on cars for rust, but
rust and corrosion are not the same thing.
But if this works for boat motors maybe you can incorporate
the basic design for alluminum on cars.
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Old 05-20-2005, 05:56 AM
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[QUOTE=jcclark]
I sure wish I could use this system on cars for rust, but
rust and corrosion are not the same thing.
[QUOTE]

Ok, now I'm confused. What is rust if it isn't corrosion? Aren't oxidization and corrosion the same thing, corrosion being a more general term?

Rich
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Old 05-20-2005, 06:58 AM
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You got your work cut out for for sure Rich.
Most Anodes are Zink. Water heaters have a zink rod in them to help prolong their life. Underground natural gas lines have one attatched as well.
Oxidation and corrosion are two different process. Kinda the same result but different. I wasn't to attentive in Chemistry class in high school so I can't really give you an explaniation.
I'm wondering mrcleaner6 if the common wire run on the yacht was connected to an Anode mounted someplace onboard?
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Old 05-20-2005, 10:44 AM
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Well, someone is going to have to show me the leadcord that goes into my woods. My posted signs are on aluminum, with cad plated lagbolts. The signs are just about to fall off from the galvanic reaction. Unless the Wood Sprites are peeing on my signs and THATS causing the white powdery residue....
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Old 05-20-2005, 12:54 PM
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Quote:
Originally Posted by Beenaway2long
Well, someone is going to have to show me the leadcord that goes into my woods. My posted signs are on aluminum, with cad plated lagbolts. The signs are just about to fall off from the galvanic reaction. Unless the Wood Sprites are peeing on my signs and THATS causing the white powdery residue....
No I think the trees must be absorbing and storing static electricity causing the corrosion, or maybe an electrical charge is being generated by fast moving squirrels running up and down?
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Old 05-20-2005, 05:42 PM
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bee

there is a zinc in the bonding system but its not inboard, it is submersed in the water. usually mounted on the transom on larger boats. small ones with outbards usually have them all over the mid and lower unit. you will even find on outboards there are small bonding straps tying the powerhead, mid housing and lower unit all together. i did goto mercury outboard school and remember doing tests with an actual voltmeter between two metals submerged in saltwater but again this was so long ago i cant remember all the details but i do remeber i was suprised how much voltage was actually generated.
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Old 05-20-2005, 07:57 PM
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Quote:
Originally Posted by rlackey
I will be building an aluminum floor for my '54 Chevy and am wondering how to treat the join with the steel at the rockers and everywhere else it comes into contact with steel. I remember studying some basic metallurgy in my aerospace engineering days and seem to remember that if dissimilar metals are in contact with each other in a corrosive environment, I'm going to get some accelerated corrosion at the point of contact.

Should I build some kind of a lip all the way around where the aluminum floorpan can sit on a rubber seal and be bolted down? What are your thoughts?

Rich
Galvanic action is going to sacrifice the fasteners whether you have a rubber seal or not. A rubber seal can reduce the amount of moisture getting to the fasteners. That moisture is the electrolyte in the battery you're building. I have a 1959 Renault 4CV which has aluminum splatter guards screwed to the lower front of the rear fenders. The Philips head screws are mostly rust, there are streaks of rust down the aluminum, but the steel fender underneath is like new. Your floor will likely not be as mistreated as those 46 year old guards. Seal the wet side as well as possible.
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