Speaking of protection, I guess at least the sides of the battery box should be protected, given the close proximity to the rear wheel well.
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Just got some scrap sheet metal I had laying around and used the MIG welder to tack it all up. The sheet metal will also give the box frame some bilateral rigidity, so that's also a plus.
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Ran all the beads...
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And grinded everthing flush on the outside for a nice clean finish. Halfway through grinding, about 2 hours, I realized it was too much work and should have left the beads showing. Oh well, couldn't leave it half grinded.
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I'm thinking this cold galvanization spraypaint would work best to protect the steel from corrosion against battery acid and such. Not sure, we'll find out how well that works. Would anyone suggest anything more appropriate?