OK, so the subframe restoration has begun.
Ignore the dirty steering rack and swaybar. New steering rack is going in later and swaybar is getting repainted satin black.
Tools I used are below. I found out a couple of things. Firstly most rust remover chemicals don't work that well. I found something that does. Napa sell an Aluminum Brightening spray for mag wheels. Any of these sprays for raw aluminum mag wheels (NOT powder coated) will work as they generally have an aggressive acid. This is possibly the most aggressive acid I've ever used so gloves and eye protection are 100% mandatory and respiratory mask as well. It strips metal so clean the surfaces typically will flash rust shortly afterwards without cleaning them with water or solvent and quickly dried, do NOT use this on zinc plated materials. I tried the Blaster Metal Rescue and the Rustoleum Rust Dissolver and no these are nowhere near effective compared to the mag wheel cleaner but they have their purpose later-on. When they say acid dipping a frame.......it's something like this but obviously much higher concentrations. Let sit for a maybe 30 seconds max & then start scrubbing with a steel brush and the rust dissolves very effectively. Takes time, but it works.
For stripping paint and heavy rust a medium grit 2" nylon 100-120 grit sanding pad mounted on a 90* air grinder worked great. Went thru about (5) to get half the subframe stripped but pricey at $1.00 ea. I'm going to switch tactis here and use my trusty new 4.5" angle grinder with the $8.99 multi-layer sanding wheel for the big flat surfaces, then switch to the smaller 2" grinder for the tricky/tight stuff. This strategy seems to be paying off as it's by far the most effective/clean way to strip paint and get the job done quickly. Any remaining rust requires a good Drill with a mounted steel wire bristle brush & abrasive cup brush. Then as mentioned I hit that with the mag cleaner acid.
I got most of the front rail of the subframe rail stripped of rust which was bad. Trying out different techniques before attempting to remove rust on the remaining sub-frame. Stripping the paint is almost mandatory at this point though the rust is predictably just in the welding joints & seams. The pitting requires the use of the wire cup brush and acid to dig the rust out. The interior of the subframe will be dealt with using a different strategy. That'll require some long rifle brushes, small chains, and any metal that can whip around inside the subframe to knock old rust and paint chips off. The goal will not to remove all the internal rust as that is physically impossible without a full acid dip. But to get enough off to treat it with the rust converter and the Eastwood internal frame coating to seal it up. Having said that, I am going to try and setup a bath using the Blaster Metal Rescue rust remover and a large pan to dip the Subframe in and see how much corrosion can be removed to start with. But generally trying to get the majority of the rust off and let the other products do their thing is the typical approach.
The welded joints & seems are kinda tricky as no amount of rust removal can get all of it out, always some is left behind. This is why the Dupli-color Rust Fix will be used. This'll convert any remaining rust to a black iron phosphate coating I can use as a first primer coat. Followed by an etching primer coat which will help prevent/delay further rusting in the future. The rust pitting will get fixed on those few spots with some filling primer and with some sanding should be good to go with a topcoat. I'll probably use a 180-220 grit final metal finish to lock the base primer and with the amount of coats I'm using it'll smooth coat that over on the final top-coat. Prior to that the entire subframe will be dropped and hung on a rack for stripping & priming/painting.
I considered POR-15 but decided against it. Most folks just use this to simply encapsulate heavy rust and somehow that seems wrong to me. If I can mechanically/chemically remove as much rust as possible that'll be best. The Pros simply media blast or acid dip and ultimately that is the best approach so I'm going for something close to that wherever possible. Functionally if this lasts 10 years then that works for me.
The picture looks bad, but the only other significant chassis rust are the (2) tow hook brackets and (1) spot next to the swaybar that was rubbing and a couple of other small spots......that's about it. I'll fix those quickly and then prime/paint. I won't be painting the engine compartment because it actually doesn't need it though the picture makes it look bad it's just mostly dirt. Little bit of cleanup on the exhaust heatshielding with solvent but again all in great shape. I was pretty good about pressure washing the engine all the time and this probably kept chassis corrosion to the minimum. With a good pressure wash it'll cleanup like new in there and I might even do some paint correction to polish that up as well.