[A/S] chassis corrosion

["nickcrowhurst" <NickandSandra@xxxxxxxxxxx>]

I recently visited "Bob's RV Used Parts", Rt 2 Box 1145, High 
Springs, FL 32643, tel. (904) 454 5733. It was painful to see once-
beautiful Airstreams torn apart and wrecked in highway accidents. 
The experience re-affirmed my determination to have a powerful heavy 
tow truck with correct load distribution. I recommend the experience 
to any newcomers like me. A further shock was seeing the rear 
chassis members exposed when the aluminium skin was ripped off in 
the accident. In Airstreams only fifteen years old there was severe 
structural corrosion of the two main lengthwise chassis members. 
Large flakes of corroded metal had fallen off, and the structural 
integrity of the chassis was clearly threatened. I thought this may 
have been caused by prolonged use in the "salt-belt states", but I 
decided to check the chassis on our 1988 Excella 25ft. This requires 
the removal of the rear fender, which is held in place by four slot-
headed bolts. These were impossible to shift, probably as a result 
of electrolytic corrosion between the aluminium fender and the steel 
bolts. I carefully drilled off the heads with a half inch HSS bit, 
centre popped and drilled out the remaining bolt shafts, and re-
tapped the holes to receive new quarter inch stainless steel 
bolts.These should be bedded in zinc chromate paste, or grease at 
least, in order to reduce electrolytic corrosion. The fender was 
then pulled off to reveal the ends of the chassis members. There was 
flaking corrosion of the exposed chassis ends, both internal and 
external, but most of this had been visible and treatable from 
within the rear hatch. I used a hammer and chisel to knock off the 
flakes, wire-brushed the area, and treated it with phosphoric acid 
and light grey Rustoleum brush paint. This left the nagging worry 
about the other 24 ft of invisible tube on each side, so I decided 
to internally coat the inside of the tubes with a rust preventative. 
I purchased an automobile rust-proofing kit from JC Whitney, and 
attached a 1 H.P compressor, as instructed. I taped a 25 ft length 
of clear plastic pressure tube to a 25 ft length of re-bar, attached 
the pipe to the compressor, and slid the re-bar and pipe down the 
end of the tube until it came to a stop at the front of the trailer. 
On the end of the plastic pipe was a spray nozzle. My plan was to 
switch on the compressor, and slowly withdraw the whole assembly, 
thereby coating the entire inner surface with the black tarry fluid. 
This was the moment all my planning came to fruition, and.....it was 
a complete failure. The compressor couldn't even get the (warmed)
fluid more than halfway down the plastic tube, let alone out of the 
spray nozzle. The spray gun was supplied with a crossed thread, and 
I ended up covered in fluid and throwing the spray gun in the 
trash.  As I had no easy access to a more powerful compressor 
(Sunday afternoon in the middle of a remote field), I jacked the 
rear of the trailer as high as possible, and poured a quart of the 
fluid down each tube. Two days later I jacked up the front and 
treated the short front tubes. This is unsatisfacory, as only the 
bottom of the tubes will be coated, but, as we say in 
England, "owt's better than nowt in a crisis"! Does anyone have a 
better method? I had assumed that commercial rust-proofers would 
have problems with a 25ft tube. Is this a recognized problem with a 
standard solution?