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Old 10-23-2017, 03:10 PM
lots2learn lots2learn is offline
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Default Abrasive Blasting

I want to know if it would be OK to use my blast cabinet to clean the little pits of rust left over after stripping disc. It uses white Aluminum Oxide and is a pressure pot type cabinet. Will run reliably down to 20psi. If I keep the angle shallow can I avoid stretching and damaging the door panel? Or should I use some other method like chemical to get ready for epoxy?


Please disregard the bottom of door. That will be replaced.

20171023_113523-resized-800.jpg primer?
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Last edited by lots2learn; 10-23-2017 at 03:16 PM.
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Old 10-23-2017, 06:40 PM
rustreapers rustreapers is offline
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Default mild rust treatment.

There are a lot of alternatives to this mild rust concern that need to be mentioned. To directly answer you question yes one treatment can be a low angle quick pass repeated several times over to bring this back to ALL white. Keep the heat down. Do not stop one any one spot for too long. the beads do help against heat distortion. A siphon jet type blaster and spot treatment on the brown rust only is also good as compared to an all out blast as mentioned. This rust appeaser less than (what) 40% of the total area. At this area amount alternatives can be implemented. Such as 80 grit sanding to reduce the area to -20% followed by chemical rust treatment plus epoxy primer. Over all you are going to get as many different options as there are responses to you question. Pick the most comfortable answers to your given scenario and hope for the best. Because you know rust never sleeps.
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Old 10-23-2017, 08:43 PM
Chris_Hamilton Chris_Hamilton is offline
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Never use a rust converter, and if you use a acid treatment be sure you know how to neutralize it (remove the acid film)before you apply epoxy. Find out more here: http://www.spiuserforum.com/index.php
If you don't hammer the panel you should be just fine. Keep your pressure low to start with, only use as much air pressure as what will get the job done. A good alternative to AO is crushed glass or black beauty/black diamond. Both are cheap at about $8-$10 per 50 lbs. I've blasted quite a few cars with crushed glass, never had an issue.
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Old 10-24-2017, 03:48 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by lots2learn View Post
I want to know if it would be OK to use my blast cabinet to clean the little pits of rust left over after stripping disc. It uses white Aluminum Oxide and is a pressure pot type cabinet. Will run reliably down to 20psi. If I keep the angle shallow can I avoid stretching and damaging the door panel? Or should I use some other method like chemical to get ready for epoxy?


Please disregard the bottom of door. That will be replaced.

Attachment 43723 primer?
I would blast that - with light fine media that is sharp. Keep moving. Go back at the end and go over again, keep moving.

Blow clean and use an acid etch - that lowers the oxidation potential of the already-rusted steel.

Long-time "Rusties" (rust-repair fellas) notice that rusted areas that have been blasted/soaked/abraded always re-rusted much more quickly in those same areas.
- unless those areas were either treated with a phosphoric acid neutralizer, or heated to 1200F.
One excellent product here:
http://www.tinmantech.com/html/must_...ver_inhibi.php

If your acid-etching primer has phosphoric in it then you are all set.

This formula for the above product was developed during WW2 as an industrial product (MP-7) and sold only in 55gal drums. It is now a "consumer" product that still may be ordered in bulk.
I have used this for 25+ years with zero problems, and on some pretty valuable clunkers. (one of the photo pairs is of a P40 drop tank that I split, saved and welded back together.)

Follow directions - grease/oil free, wipe up excess, use in warm ventilated area ....
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Old 10-24-2017, 04:54 PM
norson norson is offline
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I used a heavy duty Scotchbrite pad and phosphoric product like Kent's to clean this area in about two minutes and it was ready for primer.
Norm

P8260393.jpg

P8260394.jpg
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Last edited by Steve Hamilton; 10-25-2017 at 12:15 AM.
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Old 10-24-2017, 10:48 PM
Chris_Hamilton Chris_Hamilton is offline
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I'll say it again, if you use any acid product to neutralize the rust you need to keep it wet and then rinse with water. Never let it dry, you will then have an acid film that will severely affect adhesion especially if you are applying epoxy over top. If it does dry simply wet it again with the product and rinse with water. Improper use of acid etch products is one of the biggest causes of paint failure with modern paint systems.

If you abrasive blast then epoxy you don't have to worry about using any sort of acid etch. With epoxy there is zero need for it after blasting.

Check out this video demonstrating the adhesion of SPI (Southern Polyurethanes) Epoxy primer. And the lack of adhesion after improper treatment with an acid etch(Ospho).

https://www.youtube.com/watch?v=-yA8q4K-_Bo

Any questions about acid you can go to the SPI forum and speak directly with the President of the Company Barry Kives. He is an expert on this and all things paint related. SPI's Tech line is his Cell Phone. He personally answers any questions someone may have regarding use of a product. Super guy and the best epoxy primer on the market.
Called him once on a Sunday afternoon, I was stuck in the shop trying to finish a Corvette all over job. I had a question so I dialed him up. It rang 4 or 5 times I decided that I didn't want to bother him on a Sunday, as I knew the answer to my question just wanted a second opinion. So I hung up. 5 minutes later he calls me back! At that point he didn't know me either. After that I was sold on the customer service provided by Mr. Kives and his employees and the superior products he offers. Case in point Best of Show Pebble Beach 2015 an 1924 Isotta Fraschini was an all SPI car. Epoxy, Basecoat, and Clear, all SPI products.
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Last edited by Chris_Hamilton; 10-24-2017 at 11:10 PM.
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Old 10-25-2017, 12:45 AM
crystallographic crystallographic is offline
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Quote:
Originally Posted by norson View Post
I used a heavy duty Scotchbrite pad and phosphoric product like Kent's to clean this area in about two minutes and it was ready for primer.
Norm

Attachment 43741

Attachment 43742
Yes, and I like this phosphoric product because it requires no rinsing.
Wipe on, wipe excess, let dry and prime/paint.
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Old 10-25-2017, 06:38 AM
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RockHillWill RockHillWill is offline
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I have had quite a bit of experience with using a phosphoric treatment after both glass bead blasting (blow dry) and rock tumbling (rinse and blow dry). It has stood rust free for many months, I was able to weld and grind, then re-apply and wait until painting was done. I do not recall any negatives from using the phosphoric application.
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Old 10-25-2017, 10:56 AM
Chris_Hamilton Chris_Hamilton is offline
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Quote:
Originally Posted by RockHillWill View Post
I have had quite a bit of experience with using a phosphoric treatment after both glass bead blasting (blow dry) and rock tumbling (rinse and blow dry). It has stood rust free for many months, I was able to weld and grind, then re-apply and wait until painting was done. I do not recall any negatives from using the phosphoric application.
It's is ideal for that type of situation Will. What I am saying is that unless it is properly applied it will leave a acid film that affects the adhesion of epoxy (which is what should be used versus a acid etch primer). Here is a post by the President of SPI over at spiuserforum.com. Maybe it will help get my point across.

""My 2K high build primer cracked, you must have a bad batch"".

OK, the above pretty well sums it up, so I go last week and look at the car.
Now, this is suicide for me as every time I’m honest about something I get it shoved in my face a year later, someone will call and say my primer cracked and I read a year ago you had the same problem.
That is why the majors say nothing about acid film or Soda as they sell product when the guy reads SPI’s warnings, so they instead of researching they just buy another brand and that company could care less as they are not responsible if it comes off, it is your problem.

This is for your education and I think its an important one as there are a lot of cut and pasters out there that promote these different acids and don’t have a clue why or why not.

At least three times a week I hear, my car has been treated with acid, why can’t I use you epoxy.
My answer is always the same, neutralize it or please use one of the major’s epoxy.
You see, if a majors epoxy falls off, it must be something I did, If SPI epoxy falls off it must be the SPI stuff, being a smaller company.

OK for your education, the car was epoxied last winter by a shop and primed and blocked, eight months later cracks are showing up in the 2K primer all over the car as the shop that did the body work went out of business, so car is setting in owner’s garage.

The ex-shop owner is there and I question first the procedure on the epoxy of we used ospho or whatever it is called on the bare metal, I ask about neutralizing and got blank stares. Right away I was cut off at the knees and told the epoxy is sticking like glue but no broken spots to see??

So the owner of new shop is also there to take the car and this guy is good and does great work as known him for years and a rather famous shop so will not mention name.
Well he calls me Friday and says, epoxy at the metal is soft and the body filler at the metal is also not cured and gummy, no doubt its acid for sure as he has seen it many times also.

Yep that is what happens when you apply filler or epoxy over an acid film, outside dries great but part hitting the film does not.

There is a reason we give out these warnings and they are for your protection, not because I want practice writing, yea, I know I need it but!

Edit:
Another thing that should be pointed out here, as this car setting like it did is a rarity, if it had been painted in a normal fashion the the odds would be the primer would not have cracked.
Don't get me wrong, the primer could crack under the paint but the odds would have been better that the first few months out in sun a gassing would take effect with the uncured epoxy and body filler and a large bubble(s) would appear instead.

Maybe this will help someone from making the mistake of using a acid etch, phosphoric etch type product and not neutralizing it properly. Bet most of you didn't know that soda blasting will cause the same sort of problems unless it is properly neutralized. It is always best to blast and immediately put that blasted metal into Epoxy primer.
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Last edited by Chris_Hamilton; 10-25-2017 at 11:04 AM.
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  #10  
Old 10-25-2017, 01:16 PM
lots2learn lots2learn is offline
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I have a gallon of Ospho but decided to not use it after talking with owner of SPI a few years ago. I don't want to take a chance that I did not neutralize it properly. Anything heavily rusted will be replaced and my roof and door skins will be new.

My plan is to take some scrap panels and blast them to make sure I am not messing anything up before gently blasting mine and then epoxy priming.

Thanks for everyones advice.
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