hammerite rust beater question

[mush]

well i was busy yesterday sorting the battery tray out on the mk2 and turns out its all solid underneath due to it being sealed with the original wax.

i cleaned all the wax off and rubbed down to bare metal to prime then paint, however there was a little rust around the hole where the cables for headlight's go down into so i treated it with hammerite rust beater and got carried away and did the whole battery tray,

for some reason i was thinking i'd be able to sand this down and paint over it but theres been some horror stories on the internet saying this type of stuff if you paint over it it bubbles and re-acts with the paint<<<<<so why the hell did i do this,

ive now got to remove it all and start again. apparently its only good if you paint it on and intend on leaving it once on, the hammerite is brown and my cars red 

i was thinking it would sand down so i could prime then paint,

has anyone used this stuff? and can you use primmer on top of it?

[danny_p]

lot of hype about rust eaters.

at the end of the day they are basicly just phosphoric acid ( thats the bit that dose the work )

tbh it'll only convert the top layer of rust  so you need to mecanicly make sure the top layer is the last layer then treat it.
hen you treat it the phosphoric acid reacts with the iron oxide to produce iron phosphate job done.

then you need to wash off the resdual phosphoric acid else it will attack the primer you put on it.

[mush]

lot of hype about rust eaters.

at the end of the day they are basicly just phosphoric acid ( thats the bit that dose the work )

tbh it'll only convert the top layer of rust  so you need to mecanicly make sure the top layer is the last layer then treat it.
hen you treat it the phosphoric acid reacts with the iron oxide to produce iron phosphate job done.

then you need to wash off the resdual phosphoric acid else it will attack the primer you put on it.

cheers danny, do you reckon i should sand all this back off again? i dont know what i was thinking doing the whole tray 

i just didnt want to put paint over the top and it go dodge and look like a piece of crap,

what would you advise just take it all back off and just use normal primer and spray paint job done?

[danny_p]

sanding takes a long time,  i use a wire brush on angel grinder where possible.

if you sand back you'll clear off the phospate and be back to fresh steel in patches  no problem there.  tere is no definate right or wrong tbh

[Thom89]

Rust eaters don't work, end of!
there are only 3 ways to deal with rust 100% satisfactorily

Shot blast the rust
Cut the rust out and replace with new metal
Replace the panel

Anything else is a temporary fix

Thom