The problem here is one every older truck owner dreads: surface corrosion creeping across the underside of a vehicle that has to keep earning its keep. In this case it is a Chevy Avalanche 2500 that has been on the road for around 23 years. The good news is that the frame itself is still solid, with no holes and no rot, which the maker credits to undercoating applied years back. The aim now is to strip the flaking rust and slow its spread before it gets a foothold.
The approach is hands on. The truck sits raised on a hydraulic floor jack with 2 TON rated stands holding it steady, and the work is done with a needle scaler plus a wire brush. Light surface rust gets a quicker pass with the brush, while heavier spots get the scaler treatment. The rear differential cover, axle housing, leaf springs and chassis sections are all in scope, and even the jack stored under there picked up rust along the way.
The bumper area was the worst of it, yet it cleaned up nicely with the scaler and brush, ending mostly down to bare metal. Interestingly, once the scale came away there is a visible gap between the frame and the bumper.
The plan from here is Corroseal rust converting primer topped with woolwax. One open question remains: whether sealing over with converter first could trap pockets of rust underneath, which the maker is still weighing up.