1st sandblast then
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Senior User
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From: South Georgia
1st sandblast then
my old 56 f100 really needed some cleaning so I sandblasted a few parts. When I got down to the metal it gave a nice hazey look, but I noticed some light red shades in several areas and darker red around the dents or folds in the metal. I've always heard that when body metal is at this stage and you notice some rust you have to "kill" the rust before you can proceed. .... Is this true?
Also, I've heard about a suppos-ed rust killer called Ospho. I think its some kind of acid. Any thoughts?
Jason
Also, I've heard about a suppos-ed rust killer called Ospho. I think its some kind of acid. Any thoughts?
Jason
Cargo Master
Joined: Jul 2000
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From: Northern California
If you've sandblasted, you should not see any discolor or rust, you should just see plain metal.
I'd start by blasting the area again and see if the color goes away. Rust will usually blast off without much work, but if it's been there a while and is pretty heavy, you may need to reblast a few times.
After it's blasted, clean with Acetone at least twice, let dry for about 20 min, apply Phosphoric acid, I get mine from Home Depot $8/qt under name prime and prep. It's a green watery looking stuff, easy to spray.
allow to dry 1 to 2 days depending weather. Scuff with Scotch Brite pad
If the color is all light gray, gray, black then all is good. If you find any orange, I like to re-apply acid and dry another 2 days.
Once the whole part it treated, you should apply epoxy primer or some type of good quality primer, then coat with something, even cheap paint just to stop moisture.
If you are using a siphon feed sand blaster, I'd go over the parts several times as they don't have the speed the the pressure blasters have.
I'd start by blasting the area again and see if the color goes away. Rust will usually blast off without much work, but if it's been there a while and is pretty heavy, you may need to reblast a few times.
After it's blasted, clean with Acetone at least twice, let dry for about 20 min, apply Phosphoric acid, I get mine from Home Depot $8/qt under name prime and prep. It's a green watery looking stuff, easy to spray.
allow to dry 1 to 2 days depending weather. Scuff with Scotch Brite pad
If the color is all light gray, gray, black then all is good. If you find any orange, I like to re-apply acid and dry another 2 days.
Once the whole part it treated, you should apply epoxy primer or some type of good quality primer, then coat with something, even cheap paint just to stop moisture.
If you are using a siphon feed sand blaster, I'd go over the parts several times as they don't have the speed the the pressure blasters have.
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Senior User
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From: South Georgia
KarlJay,
Thanks a bunch! That was exactly what i needed. The Phosphoric Acid you mentioned is sold under the brand name "Ospho" here in GA. So far it looks like that stuff really works. Jason
Thanks a bunch! That was exactly what i needed. The Phosphoric Acid you mentioned is sold under the brand name "Ospho" here in GA. So far it looks like that stuff really works. Jason
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From: South Georgia
Karljay,
A friend of mine informed me that cleaning the bare metal with acetone would leave a residue on the metal that would make it hard for any filler to adhere to. What's your exxperience?
A friend of mine informed me that cleaning the bare metal with acetone would leave a residue on the metal that would make it hard for any filler to adhere to. What's your exxperience?
Cargo Master
Joined: Jul 2000
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From: Northern California
I use acetone for all my body work prep, I usually double wipe after I take a sharp nail and make cross hatchings, then I always let it set for about 20 min. When I apply the filler I push it into the cross hatchings very hard, then go about smoothing it.
I've never had any problems, some of my projects go back several years, one even 15 years and it's still holding up.
You should double wipe, one wet, one dry, wipe on wet, wipe off dry. I don't think acetone leaves a residue.
I've never had any problems, some of my projects go back several years, one even 15 years and it's still holding up.
You should double wipe, one wet, one dry, wipe on wet, wipe off dry. I don't think acetone leaves a residue.
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Rubbing alcohol (isopropyl) will remove any residue that acetone leaves. I used to work for a company that built ski boats. After they were finished we had a guy come in and pinstripe them. He would clean the gelcoat serface with acetone to remove the mold wax and anything else on there, then would go over it again with isopropyl alcohol to remove the residue from the acetone.
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From: South Georgia
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