UPDATE: Just used almost a full bottle of Rustoleum Rust Converter phosphoric acid Gel - scrubbed it in some parts several times - and covered the whole "rear bumper reinforcement" - plus some on the upper body that was hidden behind the bumper cover. I'm pretty excited - there's a set of bumper cover screws to arrive on Friday. So tomorrow I will paint over the phosphoric acid. The directions say to NOT let it dry but this is just so the paint will stay on as otherwise there is a white powder. I don't mind the white powder since if a paint is sold as a rust inhibitor paint it actually contains within it some form of acid that is just not quite as strong as the phosphoric acid. So if the paint comes off then I'll just do another paint layer later on. Better than washing off the phosphate with water since if there is any rust left then the water will just activate the rust again. No thanks! Plus I can't drive to dry off the metal since it's legally a bit sketchy to drive without a bumper cover. Technically it's legal as I still have a bumper but a cop might not know that or might debate it, etc. Not worth the potential hassle.
The acid we use will not damage your sheetmetal parts. We use phosphoric acid that's been used for decades to treat rusted surfaces for paint. Another misconception from the internet or somewhere. Let me state it again: the acid WILL NOT damage your sheetmetal panels, parts, bodies, or cabs. There are a few types of metals that the acid will damage: cast parts, spring metals, & pot metal. We can still clean cast parts and spring parts like seat springs. However, most of the cleaning on these types of metal items is done in the hot tank. Cast parts and spring material parts get only a very light acid treatment to ensure no damage is done to them. http://www.metaldipping.com/faq.php
OH yeah I forgot the spring metal is different. I'll go throw some baking soda on the spring? I think I cleaned it off pretty much already though.
This part sells for $743 online including shipping. I had part of it break off from rust. I suppose a lot more has broken off in bits over the almost 20 years this car has existed....
So I took the bumper off - the bumper COVER I mean. The "Reinforcement" is the actual steel frame piece that is bolted into the chassis frame.
It still seems solid enough - I took a steel wire brush - and there were some chunks of rust on the outside. Otherwise it seemed ok.
AFTER PHOTO:
I ordered bumper cover bolts - the OEM price is $4 per bolt!! So with shipping the "after market" price is a little over $1 per bolt (they're actually hex screws). I had two screws break off from rust - and one of the screw heads rusted out - so they all need to be replaced for sure....
AFTER PHOTO:
good thing I took the bumper cover off - can't drive with it on though. The screws arrive on Saturday hopefully.... So as per the above images - that's all supposed to be covered over with some welded on part of the bumper reinforcement. It's all rusted off over the 20 years....but the actual chassis frame with the stronger thicker steel is still intact.
So now I just need to do the phosphoric acid gel spray treatment. Will do that tonight - and see if I need to do more tomorrow - or maybe I'll just do it tomorrow.
Then on Friday I'll paint it. Then Saturday put the bumper COVER back on if the screws arrive!! hahaha.
Technically you can drive without the bumper COVER but you need the BUMPER (reinforcement)....
I had no idea a car could even be driven without the bumper as that is between the chassis frame - anyway....
The actually chassis frame part is solid - the only part that rusted off was the extra cover above the chassis frame part. So that extra cover was welded on and it's a thin metal.
The GM factory part says it's not available for an actual rear bumper and that it's been replaced by another part. But then says the replacement part does not fit. hahahaha.
Here is how it was BEFORE I did the rust drill metal brush treatment
AFTER PHOTO
AFTER PHOTO:
Here's the big part that rusted off - I had it attached with cold weld on one end. haha.
So you can see here how that's the raised up part of the Bumper Reinforcement in the very first image!!
So that part is actually upside down in my photo as you can tell from the side walls - the direction.
AFTER PHOTO:
So with the wire brush on the drill I was able to remove most of this rust. Now I just need to treat the remaining rust with the phosphoric acid gel. Then paint it all up and put the bumper cover back on!!
Prep or paint is very easy. Here are the steps our guys in the body shop take: 1) scotchbrite the surface to scuff it a little 2) wipe clean with a wax & grease remover until fully clean 3) final wipe 4) epoxy prime Those are the exact steps we use and recommend. We have some videos on YouTube showing these steps.
Phosphoric acid is also used in primers for purpose of etching ensure paint adhesion (acid etch primer) and a product called Ospho with is designed to kill rust.
Once you’ve removed the surface rust, then use 90+ alcohol to clean the surface. THEN apply Ospho and allow it 12 hours minimum to dry. THEN apply primer and paint. All in this order!
By harry johnson on March 12, 2021I sprayed as per the directions and then painted.
the rust inhibitor is phosphoric acid that is mixed with the water during the final washing process, to remove it all you have to do is wipe it down with a wet rag, then wipe it down with wax and grease remover, then wipe it with laquor thinner if desired, and your good to go.
Don't know where you'd have real acid dipping done today, but I know some racers in the Factory Apperaing/Stock Tire class that home-dip parts with parts-store battery acid. Took half the weight out of bumper brackets, battery trays, etc.
Use Enamel or oil-based paint.
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