Phosphoric acid

[ajlelectronics]

Clean it with panel wipe then sand all the steel you can get to with 120 or 180 grit, then apply epoxy primer.

Splendid advice and the most accurate in my view. If you were paranoid, then maybe an alkaline wash followed by clean water, allow to dry and then panel wipe. What epoxy did you buy? An automotive grade like Lechler 29107 is the recommended type for that purpose.

 

[Torqu-E-Cycles]

I've got spectral under 385 its a 2k epoxy, would liked to use lechler but can't get it locally and don't want to wait on delivery

 

[ajlelectronics]

I've got spectral under 385 its a 2k epoxy, would liked to use lechler but can't get it locally and don't want to wait on delivery

The TDS looks fine to me. Should do a good job.

 

[Torqu-E-Cycles]

Thanks

 

[Torqu-E-Cycles]

Suitable?

 

[Morris]

Suitable?

View attachment 395434

It will give your bodywork a great rise with a lovely texture.

 

[Dcal]

I'd worry about adding different layers of chemicals, home brew specials, or even mixing different systems, because they can have unintended consequence.

I know there will be lots of people who will have had excellent consistent results, but you don't want to be that guy.

I'd recommend, if you can, stick with what the makers recommend and they all recommend clean unadulterated steel.

The recommendations in the 385 TDS extract below, seem bang on.

"Clean steel surfaces until reaching Sa 21/2 (wet blasting) or St3 (manual cleaning or using a
power tool) in accordance with the PN-ISO 12944-4 standard; the surface after the treatment
must be free from oil, grease, dust, loose old paint coating, mill scale, rust and foreign
contaminants; the surface should exhibit the gloss of the metal substrate."

 

[Morris]

Here's a panel I'm doing at the moment (literally, photo is minutes old) and you can see the pits that are being left by the acid cleaning out the rust. This is wifeys pop bootlid, the aluminium number plate caused this patch of corrosion.

 

[Torqu-E-Cycles]

Here's a panel I'm doing at the moment (literally, photo is minutes old) and you can see the pits that are being left by the acid cleaning out the rust. This is wifeys pop bootlid, the aluminium number plate caused this patch of corrosion.
View attachment 395437

What process are you following prior to paint?

 

[Morris]

I shall treat as I described above. The panel has already been gone over with a DA using 40 grit pads. The rust will be dealt with and then wash clean with a 10% acid solution before drying with paper wipes. Once dry I will scuff with grey scotch pads, panel wipe and apply a coat of Lechler epoxy. Then any filler work it needs (it will require a touch) followed by another coat of epoxy. Then as for finish paint.
This may not be approved by some on here but I have got good results using this method.

 

[ajlelectronics]

I shall treat as I described above. The panel has already been gone over with a DA using 40 grit pads. The rust will be dealt with and then wash clean with a 10% acid solution before drying with paper wipes. Once dry I will scuff with grey scotch pads, panel wipe and apply a coat of Lechler epoxy. Then any filler work it needs (it will require a touch) followed by another coat of epoxy. Then as for finish paint.
This may not be approved by some on here but I have got good results using this method.

That is the normal and recommended method.

 

[Morris]

That is the normal and recommended method.

Except for my acid wash I think. No matter, it works for me.
Rust removal coming along, just the last stubborn bits left now.

 

[Dcal]

I shall treat as I described above. The panel has already been gone over with a DA using 40 grit pads. The rust will be dealt with and then wash clean with a 10% acid solution before drying with paper wipes. Once dry I will scuff with grey scotch pads, panel wipe and apply a coat of Lechler epoxy. Then any filler work it needs (it will require a touch) followed by another coat of epoxy. Then as for finish paint.
This may not be approved by some on here but I have got good results using this method.

Sounds and looks good to me.

Apologies if I was coming across all preachy, it was not my intention. As I tried to say, if it works it works and I'm certain you have had loads of great results over the years and have found what works for you.
I'm also certain you have found what dosen't.

I would not for a moment suggest your's is a lesser method.
There are loads of ways to skin a cat but it's interesting that most now seem to involve epoxy primer.

Some people will try loads of options and all at the same time thinking more must be better.
Sometimes they are, but sometime they work against each other and with paint it can take seconds or years to find you have a problem.
The former is bad the latter is sole distroying.

Getting all the rust out is important but so is not leaving anything worse behind, however epoxy copes with most things (just try getting it off) and phosporic acis is also well understood.
Issues can arrise when people take shortcuts or misunderstand the processes so the more people that take the time to give (and show) thier actual methods the better.

 

[Morris]

I saw nothing preachy in your post, just a statement of what works for you.
I agree with everything you have said (speaking as a rank amateur)

 

[Morris]

Gone!

 

[Dcal]

I'm also a rank amateur
I have never been paid for painting a thing in my life.

But, I do think it helps when offering advice to other amateurs if you have faced the same issues with similar resources.
However the longer you do this stuff the more resources you tend to have.
For example, when you have the facilities to grit blast at home it's easy to recommend, but not everyone can or wants to go to the bother and expense, even if they could.

 

[dave h 2]

Gone!
View attachment 395470

Now hold it up to the light and if you get pretty stars

 

[Morris]

Now hold it up to the light and if you get pretty stars

I'll be checking for perforations tomorrow, had enough for today.
Trouble is that access to the back of the panel is very restricted so it's impossible to get a dolly in to finish any repairs. It's also a thin panel at 0.7mm thick. And it's louvred (because hot rod) which just makes it worse.

 

[Torqu-E-Cycles]

Thats awesome how did you get it to strip the rust so quick!! I spent an entire day on one area and it came out probably about half as much as yours. I've spent the day welding up roof corners that were full of filler but I will dilute down to about 40% tomorrow and see if it speeds it up, just tap water?

 

[charlysays]

I wouldn't sweat it too much. I've painted over areas where I'd let it dry and rinsed and saw no obvious issues even after years.
However no paint will grip well to a thick layer of dried phosphoric acid so best to make sure the last step before painting is thorough abrading per tech sheet.
If it were me I would give the affected areas a good scrub with 10% phosphoric acid solution to get rid of any areas of thick dried acid. Dry it (compressed air and paper towels might be a good option), panel wipe, abrade per spec sheet, panel wipe, tack cloth and paint it.

The main issue with most phosphoric acid uses is that it's too runny.
Cellulose powder (e.g scolacell) as used to make Papier machet is a good thickener to keep it in place and wet. put cling film over it. Citric acid is also good used like this (bilt hamber deox gel is something like this and works really well to get all traces of rust out of craters).