Blasting

After spending almost 15 hours with the grinder I decided to bring the Volvo to a soda blaster.  Because the interior was still good the blaster only blasted the outside of the 122S.

Before soda blasting

After soda blasting

Soda blasting is better for your car than sand blasting because the soda doesn't damage the underlying metal. The only problem is that the soda doesn't remove all rust. So after the blasting it was time for some more grinding and a chemical treatment. The normal surface rust is easy to remove with the grinder but  the hood, roof and boot where "pitted".
I used phosphoric acid and Rustico to get rid of the rust pits. Not all the rust in the pits was removed by the chemicals but it went soft after the treatment and was easy to remove with the grinder without taking of too much off the healty metal.

Pitted surface of the roof

Boot - Left side done

Almost done

Soda  residue will give problems if you don't clean the metal before painting. However if you want to wait a couple of months before painting it's also a perfect rust inhibitor.

After removing the surface rust I started to get rid of all the soda dust in the car, especially inside the chassis. 

And it took alot of time...hours became days....So don't expect to get rid of the hard labour with soda blasting. There's no easy way out :-s

I used compressed air and a vacuum cleaner with a high tec (masking tape ;) attached flexible hose. With the amount of baking soda that came out of the Volvo you could easily bake cakes for the whole neighbourhood..

Cleaning the 122S

Baking soda everywere

Vacuum cleaner with hose extension to clean the chassis 

When all the baking soda was removed I started to clean the bare metal surface of the doors. The blaster told me to wash the car with warm water, add 5% vinegar, to neutralise the soda, then hit it with a pressure washer, then wash again with 5% vinegar water, then pressure wash again and dry immidiately with a blower or rag before flash rust starts. That's the main reason I cleaned one panel at a time instead of the whole car at once.

After cleaning it's best to hit the bare metal with an epoxy primer within 1/2  an hour, otherwise you'll get flash rust again. I didn't because I was still looking for the best epoxy primer. So there will be a little, almost invisible, flash rust on the doors. Luckely it's been very hot (35-40 C) and dry the last couple of days.
Sanding with 120 grit before priming will be neccessary, but it won't take too long.