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Discussion in 'General Conversation' started by Bsterker, Jul 31, 2011.
I read through this thread and finally at the end, bonding is mentioned and should have been at the beginning. Galvanic corrosion/action is the immersion of dissimilar metals in a salt solution (salt water) and the least noble metal will erode, especially aluminum.
I do not favor coating tanks with anything. Proper bonding is the only answer to preventing erosion. The simple answer to why not is that if there is a scratch, pin hole, etc., in the coating it will concentrate galvanic action in a very small spot and erode the tank in that exposed spot very quickly; this, given that your tanks and entire boat are not properly bonded. Your tanks' bonding wires should have an uninterrupted path to the least noble of metals, that is zinc.
The only way to test for proper bonding is with the boat in salt water and using a silver-silver chloride probe (red or positive wire) in the water, the probe in the positive connection on a multi-meter, then probing the fuel tank with the ground probe (that pointy thing on the end of the ground wire.) In a fiberglass boat, the reading on the meter in mili-volts should be in the 900-1100 mv range. This reading should be exactly the same when the ground probe is probed on any piece of metal in the boat that is in contact with the water such as the engine block and metal thru hulls such as a water pick up rudder, shaft, prop.
If the reading on the meter is jumping around with the probe is attached, or is more than 2-3 mv difference on say the engine block, then something is amiss in your bonding system.
I think I am boring one too many readers and will stop the "book" on galvanic action here. One more thing: you can purchase a silver-silver chloride probe on the internet and make sure you are sitting when you see the price.
I know a thing or two about galvanic corrosion but cannot figure how to attach a photo here. I wanted to post a photo of a silver-silver chloride test probe wire/thing.
Got it: drag and drop.