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tdskip
11-28-2009, 10:09 AM
Not the kind to trip on, the kind you dip or spray. Now of course, if you have any interesting stories to share by all means....

Will any phosphoric acid work for de-rusting sheet metal? Something like this from Home Depot OK to use?


https://www.homedepot.com/catalog/productImages/300/bf/bfcedd53-b667-4332-86d6-9fd0c41ca07f_300.jpg

dklawson
11-28-2009, 10:23 AM
Yes, they will all remove rust. What may differentiate one from another is whether they are formulated to leave an iron or zinc phosphate coating behind when they are allowed to etch the steel surface. I use a generic product from the local agricultural supply place. It does an excellent job. However, if the price is right... Home Depot is much more conveniently located. Thanks for the tip on where else to get the acid.

tdskip
11-28-2009, 10:48 AM
Good morning Doug. Do you wire brush off the coating before painting?

Tinkerman
11-28-2009, 10:50 AM
Most auto supply stores have an etching, metal prep type of product. You might check with them to compare whats in it and what the cost is. When I bought my car it went into storage until I finished another car that I had. I had a number of relatively new sheet metal parts that I treated with a metal prep that etched and prevented rust. Did a pretty good job, I think it was called Metal Prep, but it's been too many years for name that to be very accurate. I do know that I got it at an auto supply store.

Tinkerman

Marvin Gruber
11-28-2009, 11:01 AM
I have a gallon of phosphoric I have been working on using up for years. When I get a car in that has rust and know I won't be working on soon, I spray it down with the acid mix where ever I see rust. Also use it after sandblasting and before epoxy priming. Works well for me.

Marv

PeterK
11-28-2009, 11:24 AM
Good morning Doug. Do you wire brush off the coating before painting?


You need to wash off the phosphoric acid before painting or powder coating. I use soap and water. Then dry with air.

Metal Prep is correct name. Good memory.

Also HD PA works. I also like Rust Evaporator - left to sit overnight will remove nearly all surface rusting. Great for tools too.

But phosphoric acid products that are "rust converters" (to black iron oxide) are left alone before painting.

TR6oldtimer
11-28-2009, 05:15 PM
I use the scuff pads when applying the phosphoric acid (the acid does eat them), and I sand the metal surface with 80 grit, wipe down with a cleaner/degreaser, dry, tack cloth, then shoot.

poolboy
11-28-2009, 07:29 PM
I buy quart size bottles at either Auto Zone or Advance Auto parts under the brand name of "Right Stuff". And yeah, I know there's a gasket product by the same name. Probably confusing to the store clerks, too.

John_Mc
11-29-2009, 12:33 AM
And there's always this that I saw in another forum:
Rust removal (https://www.vwcaddyforum.com/showthread.php?s=9ec2dfb6bdeeed4f09288e3b363b970e& t=17859&highlight=vinegar)
And if you go through the drive-through at Jack-in-the-Box enough times and ask for extra packets of malt vinegar, it's free!

Brosky
11-29-2009, 06:53 AM
Is that stuff any good for cleaning rusty water stains off of white concrete?

tdskip
11-29-2009, 10:26 AM
And there's always this that I saw in another forum:
Rust removal (https://www.vwcaddyforum.com/showthread.php?s=9ec2dfb6bdeeed4f09288e3b363b970e& t=17859&highlight=vinegar)
And if you go through the drive-through at Jack-in-the-Box enough times and ask for extra packets of malt vinegar, it's free!

LOL.

How is it going John? Getting any driving in?

MDCanaday
11-29-2009, 07:00 PM
In the bad old days we used acid to etch the steel to promote the crummy lacquer prime to adhere (for a while).That was so last century,now steel is cleaned and a good self etching wash primer sets the stage for a modern 2k primer.
The phosphoric acid only removed flash rust,nothing heavy so dont think it will get into the pits and dig out the worms,it will not.There is still naval jelly for the nasty bits you dont want to sand blast.
Mostly at our shop we stay away from the haz mats as much as we can,sand is still NOT on the list.
FYI the sand most small blasters need is in the concrete section at Home Depot called "arena sand"
MD(mad dog)