Hammerite used to be the best of the best when it came to stuff for repairing cars.
But no longer.
Bought a big bottle of super-duper Hammerite evil rust remover dip, kills all known rust stone dead etc etc yada yada
Should have known there was something fishy when I couldn't see an actual ingredient listed on the bottle. Foolishly assumed I was buying something akin to the good old 'naval jelly' stuff, i.e. phosphoric acid, which always used to do the job admirably within minutes
Anyways, tried it out earlier, attempting to dissolve some rust off the MR2 - absolutely effing useless. At £10 a bottle I'd have hoped for at least some kind of reaction.. but nothing nada zilch. It didn't even lighten the slightest of surface rust. Just didn't touch it at all.
Finally found out what it is by downloading the safety data sheet from a well hidden area of the hammerite website, it's basically lemon juice

In fact if you follow the instructions and dilute the bottle to 10 litres, lemons would be a damn sight stronger