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Rusted steel after clear coat!! HELP!!

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motoguy
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Re: Rusted steel after clear coat!! HELP!!

Postby motoguy » Thu Sep 29, 2016 10:24 pm

Lots to learn.
Bulltear 6x12 w/ Proton Z axis & watertable
CommandCNC/Linux w/ Ohmic & HyT options
Hypertherm Powermax 85 w/ machine torch
Solidworks, Coreldraw X7, Inkscape, Sheetcam

michmetalman
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Re: Rusted steel after clear coat!! HELP!!

Postby michmetalman » Fri Sep 30, 2016 8:49 pm

I always thought rust started on the sides and snaked to the front. Like Bill said, almost impossible and time consuming to get it from the sides.

Countrylane
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Re: Rusted steel after clear coat!! HELP!!

Postby Countrylane » Wed Oct 12, 2016 9:28 pm

Of all the pieces we have done we have never had any rust. But I have never put steel into an acid bath. Why do you do that step? All we do is use a steel cup brush to take most of the slag off, grind everything smooth and shiny with flap discs. Use 80 grit if there's still alot of dross but otherwise 120 grit. I only wipe it clean with a brush with soft bristles and it's ready to airbrush. Even wrapping pieces in plastic for a few weeks at times doesn't rust them. And after I've got them airbrushed with Steel FX dyes many times they hang to dry for a few days before we take them in to get powder coated. Maybe it's the acid bath that causes the rust. That's what I'm thinking.

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steelfx
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Re: Rusted steel after clear coat!! HELP!!

Postby steelfx » Wed Oct 12, 2016 11:28 pm

@countrylane

The Acid Bath mentioned is used to remove mill scale, for those of us using HR steel. It is not needed for P&O or CR Steel.

The bath also removes dross, when the pieces are left in for 6-8 hrs. or longer, depending on the strength/weakness of the Acid Bath & how minimal or extensive the dross is.

Typical Starting Bath is 1:1 Water & Muriatic Acid, which is typically 31.45% Strength. In time, due to HCl gas escaping from the solution, the bath will weaken & have to be strengthened by adding more acid. Extended usage time of the bath can be accomplished by a lid or cover to slow down the HCl gas percolation.

Another easy trick for an acid bath lid is 'Plating Balls'. They're typically made from HDPe, but even ping-pong balls will work. The weak acid won't hurt them & I've seen them online for cheap!
colored ping pong balls bulk_9.88.jpg
white ping pong balls_144 ct._$7.80.jpg


The Acid Bath doesn't cause rust. It removes 100% of the mill-scale in under 15 minutes & takes the steel down to the "white' stage, which is then followed by rinsing with plain water, force-drying with clean, dry shop air, then, of course, shining the steel up with an angle-grinder & flap discs.

A Burnishing Tool (Handheld Power Tool) is also great for quickly getting the white steel shined up, but they're kind of spendy.

burnishing tool.jpg
burnishing tools & accessories.jpg


Depending on where you live & whether it's arid or humid can have a LOT to do with flash-rusting or the beginning of iron oxide formation. Anytime the Rel. Hum. is 45% or higher, the propensity for flash rust in hours, rather than days or weeks, is high. High Humidity coupled with Hot Temps (above 80°F (27°C), and rainy days can exacerbate the situation, too!

That's where VCI paper comes in really handy.. It's cheaper than dirt & will prevent rust up to 4 years! (if steel is stored indoors). Here's an article re VCI Paper, on my website: https://goo.gl/0XUxh9

Hope that helps a little.

thanks,

Bill

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Countrylane
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Re: Rusted steel after clear coat!! HELP!!

Postby Countrylane » Thu Oct 13, 2016 11:17 am

Thank you for the information Steel FX. Makes lots of sense to me. We haven't needed to go that route then because the pieces I airbrush are CR and the HR pieces get taken in for powder coating and they either sand blast or use a solution on them. This is also just a hobby for me but we have done some nice signs and brought in some income. The table makes more money cutting for fabrication, helixes for screw pilings etc which my husband does! Thanks again

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steelfx
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Re: Rusted steel after clear coat!! HELP!!

Postby steelfx » Thu Oct 13, 2016 5:27 pm

You're very welcome! :)
Bill
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