Opinions sought on best epoxy primer please.

[Favguy]

APC Pure

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That's really expensive. You can get 81% from here for around 1/3rd the cost.

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[Favguy]

I find that using phosphoric acid at high strength is counter productive, it is quite oily at high strength and is not as effective as you would expect. I used 30% for rust removal and 12% for the wash. Wipe very dry using clean paper wipes, allow to flash off the last of the moisture and scuff up ready for paint.

I agree using it "neat" generally isn't very effective for brushing on and leaving to work as it dries out too quickly and doesn't "wet" very well. However, I've found if you want to rapidly dissolve the last of the rust out of deeper pitting using a very strong solution and constantly agitating it works fast and effectively. Just be sure to wear good gloves as it stings like a bitch at high concentrations! (Oh, and cover your concrete floor under where you're working with plastic to catch any drips, it eats holes in concrete really well too!)

 

[Favguy]

I find that after a 12% wash bare steel can sit for weeks without flash rust. I really should do a test piece to see how long it will last.
As I said, I scuff up with a coarse Scotchpad before applying Lechlar epoxy and it's never given me any issues with adhesion.
I am not a professional so opinions may vary

I've a small area of cleaned steel that's sat bare since cleaning with and wiping off phosphoric acid 6 months ago in my garage! I do have a pretty damp free garage though, double cavity walls and house style roof structure. Might be a bit different in a damper or concrete type garage.

 

[Favguy]

is this what jenolite is /was?

Jenolite is indeed mainly just dilute phosphoric acid, (not sure what %, but quite low) a gelling agent, pink dye, & I suspect some form of wetting agent/surfactant

 

[steveo3002]

where you say 81% is too strong , if i was to buy 81% is a matter of adding to water to make it less %

 

[Morris]

That's what I do.

 

[8ob]

I have mixed feelings about these rust “cures”, I have given the lightly rusted box section on my gates a coat of red oxide, never been over coated and it’s still good decades later. I reckon the oxide is a better key on steel than some of these paints.

Bob

 

[steveo3002]

red oxide was good stuff , now its just red colour primer

 

[steveo3002]

jenolite says this

 

[8ob]

red oxide was good stuff , now its just red colour primer

I am of the opinion that rust stops forming on steel the second air and moisture are kept off it, no magic needed. In my book all steel needs is decent key up and a quality coat of paint, don't see the sense in all of these rust converters. Am I missing a trick?

Bob

 

[ajlelectronics]

I am of the opinion that rust stops forming on steel the second air and moisture are kept off it, no magic needed. In my book all steel needs is decent key up and a quality coat of paint, don't see the sense in all of these rust converters. Am I missing a trick?

Bob

Most paints are porous to a degree, primers especially behave like a sponge. You are right about encapsulating the part of course, no air and no water will prevent the rust. That is why epoxy primers are a game changer.

 

[Favguy]

where you say 81% is too strong , if i was to buy 81% is a matter of adding to water to make it less %

Yes, just dilute to suit. Be careful though, when diluting, you should always pour the acid into water, never pour water into acid as it can boil and splash!

 

[Favguy]

I am of the opinion that rust stops forming on steel the second air and moisture are kept off it, no magic needed. In my book all steel needs is decent key up and a quality coat of paint, don't see the sense in all of these rust converters. Am I missing a trick?

Bob

You're correct, but you are missing something with deep pitting, which is the main problem to deal with when restoring sheet metalwork. With any deep pitting, sealing out oxygen and water won't entirely stop the rust as the deeply pitted rust can still self generate oxygen (somehow, I'm not entirely up on the actual chemistry of this) and there is always some level of moisture remaining deep in the pitting to fuel the reaction. This is why it's so damned hard to permanently get rid of the stuff! Full removal followed by good. well keyed, non porous paint is of course what will give permanent success. It's not always possible or practical to fully remove though and this is where the "converters" can help by drawing out remaining deep pit moisture, whilst converting the surface of pitting to a stable form, then encapsulating it all. Very good prep is always the key here too though. Far too many think a quick wire brushing followed by slapping on a couple of coats of a converter does the job, it doesn't. You still need to remove as much rust as humanly possible first.

 

[Burdekin]

Are you planning on stripping all of the underside to bare steel?

 

[8ob]

You're correct, but you are missing something with deep pitting, which is the main problem to deal with when restoring sheet metalwork. With any deep pitting, sealing out oxygen and water won't entirely stop the rust as the deeply pitted rust can still self generate oxygen (somehow, I'm not entirely up on the actual chemistry of this) and there is always some level of moisture remaining deep in the pitting to fuel the reaction. This is why it's so damned hard to permanently get rid of the stuff! Full removal followed by good. well keyed, non porous paint is of course what will give permanent success. It's not always possible or practical to fully remove though and this is where the "converters" can help by drawing out remaining deep pit moisture, whilst converting the surface of pitting to a stable form, then encapsulating it all. Very good prep is always the key here too though. Far too many think a quick wire brushing followed by slapping on a couple of coats of a converter does the job, it doesn't. You still need to remove as much rust as humanly possible first.

Kind of flies in the face of chemistry, so more important to get some heat into the affected areas and make sure its bone dry.

Bob

 

[Favguy]

Are you planning on stripping all of the underside to bare steel?

Certainly not, as it's mainly all still sound and in original paintwork. This isn't a restoration, rather just a refreshing and preservation exercise. The bus is largely excellent, I just need it to stay that way, so I'm just doing localised surface rust removal and repainting as needed until it's 100%, to be followed by cavity wax and underbody treatment. (yet to be decided, but most likely Dynax) This is what it actually looks like, only done 8k miles!

 

[Favguy]

Kind of flies in the face of chemistry, so more important to get some heat into the affected areas and make sure its bone dry.

Bob

Yep, drier the better.

 

[ajlelectronics]

Kind of flies in the face of chemistry, so more important to get some heat into the affected areas and make sure its bone dry.

Certainly. Any rust left, especially with acids impregnated would not be my favoured method. These "converters" only affect the visible surface anyway.

 

[Pigeon_Droppings2]

Each to their own....find something that works for you.

I would recommend on your kind of project (ie a keeper) that you stick with coatings that can be visibly inspected and repaired/maintained when (ie not if) required.

 

[Burdekin]

Certainly not, as it's mainly all still sound and in original paintwork. This isn't a restoration, rather just a refreshing and preservation exercise. The bus is largely excellent, I just need it to stay that way, so I'm just doing localised surface rust removal and repainting as needed until it's 100%, to be followed by cavity wax and underbody treatment. (yet to be decided, but most likely Dynax) This is what it actually looks like, only done 8k miles! View attachment 450677

Looks great. I’d recommend Bilthamber Dynax s50then followed by Dynax UB or Dinitrol 4010 or original to keep the underside sorted.