Trailer companies have been using these bolts for almost 50 years. Fruehauf had them exclusive during the '70s. Now everyone has them. Imperial Inc., from whom I buy fasteners is a subsidiary of WW Grainger, has been around along as I have. It is a tried and proven product. In the 40 something years I have been using these bolts I have never had a bolt come loose because of failure of the nylon washer. Back in the '70s Strick trailers used a stainless steel washer to Isolate the bolt head from aluminum. After a few years of exposure tp salted roads, the stainless steel washer split leaving about .040 gap and it wasn't long after that the bolt broke. As far as isolating the bolt from the aluminum bottom rail, the bolt fits tight enough that salt spray does not get between the bolt and the aluminum. We have disassembled some of these bolts after years of service to do other repairs to trailers. And the bolts came out with no evidence of the white powdery electrolysis. In fact it was tempting to reuse the bolts. I can pull 3/8 Huck bolts and I can buck rivets 3/8 and larger. But I prefer these bolts over Hucks or rivets. I wonder of if you are criticizing a tried and proven product from experience for from theory.
