I've been getting a lot of advice from a buddy who is an A&P mechanic with the airlines. For years he worked in a refit facility doing to 727's/737's etc metal work similar to what we are all doing to our Airstreams. He has suggested that any time I put a fastener (that is not aluminum) thru an aluminum part on the trailer, to use an aluminum washer. The idea is that you sacrifice the washer instead of the fastener or the aluminum part on the TT. Somebody suggested that above. In the case of my TT, this will only be a real problem around the perimeter in the U channel as the new floor goes in. The bolts and screws that are there now will need to be replaced. It appears that all are steel, and all have corroded to some extent. I say corrosion, because a large portion of it is due to water leaking in.
Just my 2 cents.
Jim
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“Never underestimate the power of stupid people in large groups.....especially when they're near a ballot box.” --annon.
My gosh, reading this thread made me think at first that I was on the forum for vintage MG sports cars (and their owners). Had to pinch myself to get up to speed: No, dummy, this is about Airstreams!
Lynn
What you say makes sense, but then I started thinking--why is the sacrifice of a washer even necessary? Why not use a washer of some other inert substance (nylon, plastic, rubber, copper, brass, something?) that could act as an insulator, stopping the sacrifice of the washer, as well? If there is anything inherently better about an aluminum washer, what about painting them before use (por-15?)? Would you mind asking your mechanic friend about this if you don't know the answer already?
Just curious, since trying to figure this out as well...
Mary
Quote:
Originally Posted by Jim & Susan
He has suggested that any time I put a fastener (that is not aluminum) thru an aluminum part on the trailer, to use an aluminum washer. The idea is that you sacrifice the washer instead of the fastener or the aluminum part on the TT.
Mary,
For the most part, the issue here is controlling the corrosion so it doesn't damage important items. Unless the trailer is kept in a perfect environment, it is going to corrode. As soon as oxygen gets to any raw metal, it is going to corrode. Raw metal can be intentional, like aluminum castings, or it can be incidental like rock chips, clearcoat failure, and raw metal edges from fabrication. Add water (humidity, fog, rain, snow, salt water...) and the corrosion is accellerated. By keeping oxygen and water away from the raw metal, thru painting, clearcoating, waxing, etc. you greatly reduce the tendacy to corrode. What we're trying to solve is how to control the corrosion by sacrificing other metals.
When dissimilar metals are in contact with each other, the more noble (less likely to corrode "example: gold or titanium") metal will transfer excess free ions normally part of the corrosion process to the lessor noble metal (example: zinc). Check out the galvanic chart connection given earlier. This causes accellerated corrosion in the lessor noble metal with very minimal impact on the more noble metal.
Zinc is one of the most likely to corrode metals commonly available today. The beauty of zinc is that it can do a lot of corroding before it is consumed, hence my suggestion that solid zinc washers might be used as sacrificial metal to protect the aluminum and steel. I could see how aluminum washers could be consumed quickly, causing connection failure. If you make the washers so they can't corrode by painting them, the corrosion is goes to the least noble metal available which is either the aluminum or stainless steel.
You probably already have an example of zinc in corrosion on your trailer. Check out the safety chains at the hitch connection. If your chains are like mine, they are galvanized steel. In places, the zinc is gone and the steel underneath is starting to rust but not quickly. The zinc is being sacrificed to protect the steel.
Last edited by Bob Thompson; 04-21-2005 at 02:27 PM.
Here is another good source for stainless steel. I used this company many times when I was building wood drift boats in Alaska. Their prices are really good and they will ship. They don't have a website, just call them and they will get you a price.
Northwest Fasteners Inc
PO Box 92038
TillicumWA98492
253-582-1671
Fax 253-581-3131
One more note about this thread, which was not mentioned. That is an electrical current. The tear drop side markers are grounded to the body. So we have a current flowing from the maker lights to a ground through the body. Add dissimilar metals into the formula and it can cause additional corrosion. To fix this in my trailer, I am going to run a ground wire to all the lights that will ground right to the frame. Just food for thought.
Did you know that the old Skyliner TV antennas can have a "dissimilar metal" corrosion effect on the aluminum roof? We just discovered this on our roof. The pitting was so bad that the roof was like swiss cheese, and leaking!
I've got the same thing on mine. My plan was to mount a new antenna to the same spot...re-use the hole for the shaft/crank, but perhaps that's not such a good idea (?).
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