Heavy Surface rust removal & metal prep to prime?

[rockytopper R.I.P 5-13-2017]

In an an attempt to find good metal to determine the extent of lower qtr patch I started my first ever battle with decades of exposed metal. Apparently someone stripped this car in an attempt to do body work years ago and never finished it. After 10 hours of hard sanding and 2 application of naval jelly rubbed in with steel wool I'm starting to make progress. There is still some pitting that needs more work. My current plan is to continue with the naval jelly and DA. I saw guys use hand held blaster to spot blast the remaining pits what are your thoughts on this?
Thanks
Rocky

[Rick_L]

This is a judgment call. The pits that you show in your last photo can usually be treated and saved. But where's the line? Hard to describe. My thought is that if the pits are small you're okay. If you have a pit that shows a difference in metal thickness over the pit, then you need to investigate further. I have welded up some of this type of pit. If you can't weld it without blowing holes, then you need to replace with fresh metal.

Maybe someone else has some guidelines.
'

[chevynut]

If you decide to blast it you risk stretching the metal and causing warpage. I would keep trying to remove it using other methods, like chemicals and brushing. If it's close to a formed edge, blasting is probably safe...but not in a flat area.

[rustay56]

Rocky, I would use a spot blaster if you have one,a pot blaster would be better as you have a big area to do and you want to get the metal clean and into epoxy primer as quickly as possible. I'm not sure what Naval Jelly is as we don't have that product in Australia how ever I use Phosphoric Acid and a red scotchy and get what looks like the same result. Once the rust has been neutralized it's easier to remove. Chevynut is correct in saying you run the risk of stretching metal when you blast but that usually happens because people try to remove paint(sometimes multiple coats)/primer and rust at the same time which generates to much heat,hence stretching.You have reduced your chance of this by removing paint first,this is I.M.O the best way to proceed as you get a visual on how much rust you actually have.If you have done blasting before disregard my advice, With the pressure set aim the blast nozzle about 6 inches off the concrete at 45 deg and open the feed valve slowly until you see the top of the concrete start to pit and break up and that is about right for blasting panel steel.Now start at the one end of the panel with nozzle @ 45 deg and approx 6in off panel and move forward working the nozzle in a small circular motion,don't be too concerned if you don't remove all the rust on the first pass.(Resist the temptation to stay in one spot and work it until clean.Heat=stretching). Once you have finished going one direction repeat process but from the opposite direction.this should get most of the rust removed.On stubborn areas you may have to try coming from the top and bottom with nozzle,but eventually you will succeed.Just remember don't get the panel to hot.Think of it like thousands of little pick hammers tapping away in one spot.This is where the pot blaster is better because you don't have to stop and refill so often.Once finished blow down panel thoroughly with DRY air and epoxy prime.then sit back and admire your handy work. Only 12 panels to go. Roof last please,you will have your technique mastered by then. Good Luck.

Regards Andrew

[rustay56]

Just had a thought,if you have a product over there called EVAPORUST you could use that.but it only works while it is wet( the panel )as soon as it dries the process stops. It is water soluble and bio-degradable. It will make that panel look like new (with pits).Now the down side,you have to set up some sort of spray system to keep the panel constantly wet and also recover fluid to reuse,and enclose to stop evaporation,but it does work and no chance of panel damage.Also it will not remove paint so panel must be stripped of all coatings.It is expensive but you keep recovering and reusing until it eventually breaks down and doesn't work anymore then throw it out.You can also let your rusty parts soak in it,it's like molasses but works faster doesn't stink.

Regards Andrew

[MP&C]

I've never been a fan of the fix-all, cure-all products: rust converters, rust encapsulators, paint over rust, etc. Fix it right, fix it once. A bit of rust converter dried up in the bottom of some of those pits becomes a nice deposit of acid to come back and haunt you later in the form of paint delamination. My preference would be a fine grit garnet type abrasive, low pressure, and some common sense. The biggest cause for failure in using media blasting is too much pressure, too much impatience, and too large of media. If the pits are too deep and/or too troublesome to clean, resort to new metal. Paint products today are much too expensive to take a short cut at this stage in the game. Ie: it's much cheaper to fix the problem now before the paint goes on..


Also, before attempting any repairs of the quarter I would recommend stripping the paint/filler/etc from every inch of what you have. You may be pleasantly surprised and find what you see now is the only damage. If your luck runs like most of us, there are more things lurking beneath prior repairs that will need attention as well. At the point of finding additional damage, you may find a full quarter a better solution to resolve ALL the issues. Better to find out that need prior to spending a bunch of time welding in a patch..

[rustay56]

I agree with you on the cure all products Robert,but i have used evoporust many times,once panel is clean of rust, wash down with water to remove residue, dry off panel.I then give it a quick wip with the blaster and epoxy prime.Works good for motorcycle tanks, fill to the top and leave for a few days.
I just re read this post,sounds like I'm doing a commercial for them .

Regards Andrew

[chevynut]

Lots of people mistakenly think sandblasting generates heat, and that's what warps the panel. That's absolutely not true. There is very little if any heat generated, and surely not enough to warp a panel. When blasting through paint, you're not even touching the metal and nothing can happen to it. The warpage comes from the peening of the metal from the sharp abrasives. It stretches one side of the metal, causing that side to bow upward toward the blast nozzle. If you think that can't happen take a 1/8" thick piece of steel and a center punch, and make a bunch of marks on one side of the steel with the punch. It will bend. A guy on the other site had a trunk lid that was blasted from the bottom side, to clean up the inner structure. The blaster hit the topside sheetmetal through the triangular openings in the inner brace, and there were significant dips on the top of the trunk lid. That was from peening the bottomside...and this was supposedly a professional sandblaster who did this.

I have seen this happen with my own eyes and you have to be VERY careful. I was blasting the brace on the back of my Nomad's hood which was perfectly straight prior to blasting. I used a fairly fine silica sand and not that much pressure. I tried to avoid blasting the underside of the hood sheetmetal, but I did hit it slightly at the edge of the brace. After primer and blocking, I noticed a dip on the top of the hood the full length of the brace. It baffled me as to what it was until I was looking at some pictures and noticed a slight blasting of the underside of the hood skin. I had to bodywork that entire area back up to be able to use Slicksand to make the dip go away. I had a similar thing happen when I blasted my roof brace at the b-pillar, but it was lighter and one coat of Slicksand took care of it. ALWAYS use some sort of mask when doing blasting on a brace like this, so you don't hit the flat sheetmetal.

I don't care how little pressure you use, you will probably get some stretching of the metal if you use a hard media like sand. Whether that stretching is enough to cause significant warpage is the question. Light pressure may prevent it but may not remove rust effectively. You have to be careful.

[rockytopper R.I.P 5-13-2017]

Andrew naval jelly has Phosphoric Acid as its active ingredient. The US navy developed it to fight rust on ships as I understand. It is thick so very easy to apply and doesn't run off the panel. I plan to continue to try and remove as much as I can before resorting to any form of blasting. The example I was referring to for blasting was only done in dime size spots as needed directly on the pits to remove any remaining rust after all attempts to remove it by hand as I have mentioned was done. I was planning to remove all paint and rust on the exterior by hand with a DA and brush etc but I was planning to have the floors, dash, inner fenders, inside fenders, inside rockers , firewall, and frame dustless blasted after I get the main floor removed and body off frame. That could also include these areas that have been left exposed and have deep rust.
However from what C/nut is saying perhaps any form of blasting should be avoided. I am getting handy with the wire wheel lol.

[Rick_L]

rocky, blasting is fine for, and actually preferred, for any high crown panel. That would include floor, firewall, door jambs, inner door panel, inner quarter panels, etc.

[DocHarley]

I was the guy on another site who had blast damage on my trunk lid. Remember Robert? What a nightmare.

I had some pitting on my floor, used a heavy duty wire wheel, worked great to remove the rust from the pits.

[Rick_L]

if you have a product over there called EVAPORUST you could use that.

I would speculate that EVAPORUST is a phosphoric acid product like naval jelly. There are many commercial names for this kind of product - Picklex 20, POR metal conditioner, etc., and many more. Some of the paint companies like PPG and Axalta (formerly Dupont) have this kind of product too. They all work the same way and have similar ingredients - they really only vary in the strength of the solution out of the bottle.

[rustay56]

Rocky, thanks for the explanation on Naval Jelly,I've heard you guys talk about it but never knew what it was. I'm now informed.
Rick, Evaporust has no acids,alkalies,bases or solvents,it wont effect rubber,plastic,copper,brass,aluminum,p.v.c or vinyl, we used to have a tank in my town large enough to submerge a car body full of Evaporust. we used to throw all our panels in and go back and pick them up in a couple of days, I would just reach into the tank up to my arm pits and pull the panels up for an inspection.That company closed down due to poor management.I am currently trying to set up a small tank big enough for individual panels to soak in. At approx $240 /20 litres or 5 gallons I need to make it just big enough for my largest panel (tri 5 hood) to minimize cost.
Laslo,you are correct about metal stretching upward,a good example would be using a spot blaster with a recovery bag on to do some rust spots on a vehicle roof/turret.it requires you to blast directly at the panel in order for the recovery bag to work. when removed there is a raised spot on the panel where you have blasted. That being said I blast all my panels on the face side only,after I have removed all coatings and have never had a problem with stretching or deformed panels. I currently have a new Real Deal Steel 57 sports coupe body on the rotisserie,I will strip both qtrs and turret then over the course of a week we will blast and epoxy inside and out.I will take some pics as the job progresses and post.probably should start a thread and do a start to finish on it.

[MP&C]

I was the guy on another site who had blast damage on my trunk lid. Remember Robert? What a nightmare.

Yep, sure do. That was a good learning tool for all of us...

[Bitchin'57]

I would speculate that EVAPORUST is a phosphoric acid product like naval jelly. There are many commercial names for this kind of product - Picklex 20, POR metal conditioner, etc., and many more. Some of the paint companies like PPG and Axalta (formerly Dupont) have this kind of product too. They all work the same way and have similar ingredients - they really only vary in the strength of the solution out of the bottle.

Evapo-Rust doesn't have any acid in it. It removes rust by a chemical process called chelation. I'm not a chemist, so I can't explain the process, but I can tell you this much, I've used Evapo-Rust a few times, and its amazing stuff. I have a 5 gallon can of it, and its totally safe to stick your hands in. It removes only the rust. It is harmless to the base metal. I put two pairs of extremely rusted bucket seat slider brackets into the 5 gallon can of Evapo-Rust, and 24 hours later, they were 100% rust free. I have pics to prove it.