If my son and I start to remove the old finish from our car (sanding) as we progress on a daily basis and uncover bare metal can we use etching spray can primer to cover the exposed metal till we get enough to spray our first full cover????? Also can someone give me a good brand of air sander to purchase--thanks Steve
start of body work
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805moparkid
Slant and AFX Guy
for the strip i like to use an 8" mudhog with 40 grit on it, then DA with 60 grit and epoxy prime. you can knock out the whole car that way and have it primed in 6 hours or less with two people.
DaveBonds
Garage Trash
It's a rotary sander that is typically used in collision repair shops for cutting body filler quickly.
It's made by a company called Hutchins and it's not cheap. There may be other brands that people use the name as a reference to, but I know the name under that brand actually being used. I've also heard the term mudhog used for an air file, which is a reciprocating sanding tool that uses sanding board paper. I'm betting this is what he's referring to.
If you are doing this as a hobby, don't bother with an expensive sander. Just pick up a 6" DA (dual action/ orbital) from Harbor Freight, Tool King or the like. They are cheap, but they will work fine with a good pad. Don't use the skinny backing pad that they come with. Get something from a paint supply shop that suits the paper you buy.
I think epoxy primer is good for bare metal, but I don't like using primer on anything coarser than 80 grit on bare metal and 150 on filler. The scratches can show up later, unless you are willing to let the primer sit after sanding, to guide coat and re-sand.
I went through a roll of 80 grit on a 6" DA sander to knock down all of the paint to bare metal on the Scamp in a day, on my own.
Acid Etch primer is a good thing to put down, before using a urethane primer. Epoxy primer can go direct to freshly sanded metal.
I prefer polyester primer, because of it's high build and sand scratch coverage, coupled with its ability to give a uniform, chemical surface that bonds to metal and filler. It helps keep areas where filler is used from shrinking or moving at different temps that the car is subject to, on its own, because the entire surface is alike.
It makes a good barrier for a 2nd coat of urethane primer to go and helps get the car extremely straight, because you can block sand it with a 2' long board, over gaps, with anything from 150-320 grit, before a 2nd coat of primer, for final fine sanding.
It also replaces the need for polyester putty/ glazing putty on filler areas, as long as you are vigilant on removing air bubbles from the filler, when mixing it, by spreading it from the top on the mixing board. You can go back in and correct pinholes in the filler, if you find any, by taking some of the polyester primer with your glove and dabbing it over the pinhole a few times. It sands out just fine.
If I were going to prep a car for a complete paint job, I wouldn't hesitate taking it all down to bare metal, unless I had no place indoor to store it. You will end up with a nicer finish in the long run. The more uniform the surface is on a molecular level, the less likely you are to see areas changing independently after time.
It's made by a company called Hutchins and it's not cheap. There may be other brands that people use the name as a reference to, but I know the name under that brand actually being used. I've also heard the term mudhog used for an air file, which is a reciprocating sanding tool that uses sanding board paper. I'm betting this is what he's referring to.
If you are doing this as a hobby, don't bother with an expensive sander. Just pick up a 6" DA (dual action/ orbital) from Harbor Freight, Tool King or the like. They are cheap, but they will work fine with a good pad. Don't use the skinny backing pad that they come with. Get something from a paint supply shop that suits the paper you buy.
I think epoxy primer is good for bare metal, but I don't like using primer on anything coarser than 80 grit on bare metal and 150 on filler. The scratches can show up later, unless you are willing to let the primer sit after sanding, to guide coat and re-sand.
I went through a roll of 80 grit on a 6" DA sander to knock down all of the paint to bare metal on the Scamp in a day, on my own.
Acid Etch primer is a good thing to put down, before using a urethane primer. Epoxy primer can go direct to freshly sanded metal.
I prefer polyester primer, because of it's high build and sand scratch coverage, coupled with its ability to give a uniform, chemical surface that bonds to metal and filler. It helps keep areas where filler is used from shrinking or moving at different temps that the car is subject to, on its own, because the entire surface is alike.
It makes a good barrier for a 2nd coat of urethane primer to go and helps get the car extremely straight, because you can block sand it with a 2' long board, over gaps, with anything from 150-320 grit, before a 2nd coat of primer, for final fine sanding.
It also replaces the need for polyester putty/ glazing putty on filler areas, as long as you are vigilant on removing air bubbles from the filler, when mixing it, by spreading it from the top on the mixing board. You can go back in and correct pinholes in the filler, if you find any, by taking some of the polyester primer with your glove and dabbing it over the pinhole a few times. It sands out just fine.
If I were going to prep a car for a complete paint job, I wouldn't hesitate taking it all down to bare metal, unless I had no place indoor to store it. You will end up with a nicer finish in the long run. The more uniform the surface is on a molecular level, the less likely you are to see areas changing independently after time.
gtmopar
Phuckin A!
40 grit to strip? Maybe if the car has 2" of mud on it. Unless you plan on skimcoating the entire car to fill in the gouges from the sand scratches I guess that's ok. 80 grit it what I've always used. Granted if there are areas of thick bondo, grab a hammer and chisel and knock that **** off.
So get a good da and maybe a orbital sander like the mudhog,I know you don't want a grinder but what I'm understanding a mudhog is a orbital sander that doesn't just spin it orbits just like a da sander just on a grander level--Steve
DaveBonds
Garage Trash
One thing you can do, if you are worried about storage or being somewhat weatherproof, on a temporary scale, is to sand one panel to bare metal at a time and coat with epoxy primer.
Acid etch/ wash primers are only used in a dust coat. They go on very lightly and are not going to keep the area/ panel from rusting if exposed to water. Typically, I use Acid etch primer as an adhesion promoter and surface prepping agent for urethane primer, just before I use the urethane primer. You shouldn't need to sand acid etch. It's a chemical bond and should be followed by another primer, after it's flashed/ set up.
Acid etch/ wash primers are only used in a dust coat. They go on very lightly and are not going to keep the area/ panel from rusting if exposed to water. Typically, I use Acid etch primer as an adhesion promoter and surface prepping agent for urethane primer, just before I use the urethane primer. You shouldn't need to sand acid etch. It's a chemical bond and should be followed by another primer, after it's flashed/ set up.
gtmopar
Phuckin A!
Use a good self etching primer from SEM to cover the small spots. The right way to do it is strip the entire car and epoxy prime it before doing anything bodywork wise. The epoxy prime will protect the metal from rust. Do your bodywork over the epoxy primer( scuff it real good first) then when all of your bodywork is done then you put it in filler primer. Then the fun of blocking and priming, blocking and priming 10 times until its perfect then you are ready for color. Yea just get yourself a cheap DA from harbor freight and a big roll of 80 grit DA paper from autobody tool mart and you will be on your way.
DaveBonds
Garage Trash
A mudhog is a planetary geared down rotary sander. Not orbital.
Just grab a DA from a cheap tool supplier. I use them all the time and turn out show winning paint jobs. There is nothing wrong with them for complete paint jobs.
If I were a painter or prepper in a collision shop, I'd buy a nice, single hand palm DA sander made by Dynabrade, but I don't spend enough time in my shop to justify spending $300 on a sander.
The same goes for the Hutchins Mudhog.
Again, air files are commonly referred to as mudhogs.
If a car that I'm working on has a significant amount of body filler in it, I use a torch and paint scraper to burn the resin from the filler and let the filler crumble away from the body with the putty knife. Way cleaner, easier and quicker than sanding old filler off.
Just grab a DA from a cheap tool supplier. I use them all the time and turn out show winning paint jobs. There is nothing wrong with them for complete paint jobs.
If I were a painter or prepper in a collision shop, I'd buy a nice, single hand palm DA sander made by Dynabrade, but I don't spend enough time in my shop to justify spending $300 on a sander.
The same goes for the Hutchins Mudhog.
Again, air files are commonly referred to as mudhogs.
If a car that I'm working on has a significant amount of body filler in it, I use a torch and paint scraper to burn the resin from the filler and let the filler crumble away from the body with the putty knife. Way cleaner, easier and quicker than sanding old filler off.
gtmopar
Phuckin A!
Yea just do it a panel at a time and don't rush it!!! It is a long tedious process but its really rewarding in the end, especially when someone asks you " who did your body and paint " and you tell them "I DID BITCHES!" That is the best! Post pics and if I can be of any assists nance let me know or PM me if you don't want to hear 50 different ways to do it.
DaveBonds
Garage Trash
If you use body filler over epoxy primer, be careful about your filler selection and make sure that it is suitable with the right additives to adhere to paint and primers. Most fillers that are on the cheap end of the shelf will not.
Evercoat makes a good one, but Z grip will not bond to primer. Rage doesn't either, last I knew, but I don't know if the formula has changed.
Crest makes a filler called Shark Bite that sticks to everything. It's about $40 per container, though.
I use Z grip and other fillers that are made for bare metal. I strip each panel, if not the entire car and right before I do filler work, I hit the entire panel or area with 80 on a DA, so I know the surface of the metal I'm working with has been cut clean of any oxidation or rust that I can't see.
Evercoat makes a good one, but Z grip will not bond to primer. Rage doesn't either, last I knew, but I don't know if the formula has changed.
Crest makes a filler called Shark Bite that sticks to everything. It's about $40 per container, though.
I use Z grip and other fillers that are made for bare metal. I strip each panel, if not the entire car and right before I do filler work, I hit the entire panel or area with 80 on a DA, so I know the surface of the metal I'm working with has been cut clean of any oxidation or rust that I can't see.
805moparkid
Slant and AFX Guy
sorry the real name is a vertical sander, ive always heard it called a mud hog. they have them at HF to...
http://www.northerntool.com/shop/tools/product_200112074_200112074?cm_mmc=Google-pla-_-Air%20Tools-_-Air%20Sanders-_-158320&ci_src=17588969&ci_sku=158320&gclid=CJ6nu6-F47kCFaVxQgodVGIAcQ
with the 40 grit your going to just take the paint and mud off, takes one pass, just till you see metal coming thru. and yes the only way to get it flat is to skim coat it and cut it. you'll here alot of people tell you skim coating is bad but they dont cut it enough. you have to cut it and get metal just to come thru and you'll be in good shape.
http://www.northerntool.com/shop/tools/product_200112074_200112074?cm_mmc=Google-pla-_-Air%20Tools-_-Air%20Sanders-_-158320&ci_src=17588969&ci_sku=158320&gclid=CJ6nu6-F47kCFaVxQgodVGIAcQ
with the 40 grit your going to just take the paint and mud off, takes one pass, just till you see metal coming thru. and yes the only way to get it flat is to skim coat it and cut it. you'll here alot of people tell you skim coating is bad but they dont cut it enough. you have to cut it and get metal just to come thru and you'll be in good shape.
DaveBonds
Garage Trash
I always skim everything, because it catches things I can't always see or feel.
People are afraid of body filler for the wrong reasons. I agree.
People are afraid of body filler for the wrong reasons. I agree.
805moparkid
Slant and AFX Guy
exactly!
things i should add:
dont spray high build directly on bare metal unless its an acid etch primer like the PPG NCP primer. it will lift AFTER its color sanded, buffed, and delivered...
strip and blast bad rust spots, acid wash the rest and then 60/80 DA and then one wet coat of black epoxy prime.let the epoxy tack off for an hr (70* with 10% humidity) anything with colder temps or higher humidity and it will take longer.
rough out your first mud coat and 80,then spray your high build right over the top of it. after than long block the primer till you just see the black of the epoxy. stop and work any obvious lows, level and reprime.
should take you two primes before you no longer need mud work. then you can 80 long block and prime three times.
a picture like that ads more cred to someones "this is how you do it" than anything...
DaveBonds
Garage Trash
It depends on the poly primer. Evercoat suggests not doing it over anything, other than fresh sanded metal, while other brands that I've used require acid etch.
80 + poly primer and a long board + final prime (epoxy or urethane) and it's nice.
I've been experimenting with hand sanding my final color sanding vs orbital/ trizact and I'm going to try it on a bigger panel with an 8" durablock. The orbital sanding looks great, like what you've got showing in your pic, but the hand cut areas that I've been experimenting with so far are as straight as a laser.
I've also found that it makes all the difference when you spend more time with the wool pad, before moving up to finer compounds and foam pads.
Woods74
Broke Senior
Wd-40, Not a big fan of the skim look, makes the car look unnatural and bubble like.
luckysgarage
Well-Known Member
Whatever products you decide to use, make sure to read the tech sheets for that product. It will give you their recommendations for application of the product. Very help full. Usually can be found at the products website.
AdamR
Big Member
I agree with Moparkid. I wont do an old car without stripping it to bare metal. If you dont have time do strip the entire car and prime in a day, do a panel or 2 at a time and epoxy them.
ok-thanks guy's-I think i got it,if we do the hood or trunk or doors take it down to bare and spray epoxy primer on it to "seal" the metal and it can sit then till we really start to tackle the project---Steve
I hate to ask this but I will put my neck out,Can you get a quality product (epoxy primer) in a rattle can or not????? or are we going to be mixing the primer little batches at a time--Car will NOT see weather during this--Steve
AdamR
Big Member
dont use spray cans, It will cost a fortune and you will have to re strip it.
72ScampTramp
Scamp Tramp
yes dont use spray cans. Another option is media blast. Its getting more affordable but still will cost you.
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