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mill scale

 
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okjayhawker
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Joined: 31 Jan 2011
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Location: Laverne, Oklahoma

PostPosted: Sat Jan 31 15 9:07 am    Post subject: mill scale Reply with quote

I cut a piece of 3/8 plate to go on my grill for some griddle cooking, I spent an hour wire brushing the metal down to shiney. I tried seasoning it, but it does not seem right, did I make a mistake removing the mill scale?

Can it be salvaged or do I need to start over?

Thank you in advance.
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jess
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PostPosted: Sat Jan 31 15 7:08 pm    Post subject: Reply with quote

My guess is you are just polishing the scale. A couple things work none of them fun. Acid etching works, but then you have the cleanup. Blasting will do it with very aggressive media & plenty of pressure. This size project I would get plenty of 36 grit paper & some elbow grease. I'm sure someone will be along with some better ideas. Good luck...
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k.a.m.
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Joined: 12 Dec 2007
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Location: Southeast Texas.

PostPosted: Sat Jan 31 15 7:55 pm    Post subject: Reply with quote

I need to know first.
Was the steel new or old?
If new were you trying to remove the mill scale?
If old were you trying to clean up rust and pits?

If new and you were trying to remove mill scale then a wire brush is no match for it let alone one 40 grit flap disc, like jess said you are just polishing the mill scale and a light sweep blast would be my choice. This way you can come back with a 40 grit flap disc and shine that puppy like a new nickle.

If the metal is old the same blast will work but the finished product is not as nice if the metal has some pitting.

The best griddle material is cold rolled steel, it does not have mill scale and only requires a light wash when new to remove the protective oil.

So with all that what have ya got? Very Happy
I hope this helps. Very Happy
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okjayhawker
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Location: Laverne, Oklahoma

PostPosted: Sat Jan 31 15 11:11 pm    Post subject: Reply with quote

The plate of steel has been out in the weather for about a year, and had a light coat of rust on it, but was basically new. I lightly brushed it with a wire wheel on a grinder to remove the rust, but then decided it would be best to remove the mill scale, which I am positive I did.(took some time)

I guess my question was was it a mistake to remove the mill scale, or is that what you want to do to make a griddle?

Any advice on seasoning would be appreciated, I put some olive oil and put the heat to it last night, but I think I got it too hot to quick, and kind of scorched it along the middle where the burner is.
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gandrfab
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PostPosted: Sun Feb 01 15 2:10 am    Post subject: Reply with quote

I'm with Kam, you will not remove the mill scale with a wire brush, even with a wire brush wheel on a big hand grinder.
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jess
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PostPosted: Sun Feb 01 15 5:17 am    Post subject: Reply with quote

I know some people that work in shipyards. Their advice is to do as they do & leave the plate out in the elements for 6 months or so, so the oxidizing process ( rust) can start under the scale & help loosen it...
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k.a.m.
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Location: Southeast Texas.

PostPosted: Sun Feb 01 15 7:48 pm    Post subject: Reply with quote

okjayhawker wrote:
The plate of steel has been out in the weather for about a year, and had a light coat of rust on it, but was basically new. I lightly brushed it with a wire wheel on a grinder to remove the rust, but then decided it would be best to remove the mill scale, which I am positive I did.(took some time)

I guess my question was was it a mistake to remove the mill scale, or is that what you want to do to make a griddle?

Any advice on seasoning would be appreciated, I put some olive oil and put the heat to it last night, but I think I got it too hot to quick, and kind of scorched it along the middle where the burner is.

Mill scale is a short term protective coating on hot rolled steel. Over time and with heat it will pop off so yes removing the scale for a griddle would be my choice.
As far as seasoning goes I would clean off the scorched olive oil first, then depending on how large a piece we are talking would determine how I seasoned it.
I prefer Crisco to season with, wipe down the steel and place in your oven on 350° for about 2 hours.
Another way is to place it in your smoker with a good hot fire and season it.
Direct high heat in one spot too long will result in scorching, remember seasoning is a slow process not done quickly.
What size griddle are we talking about?
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Wreckless
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PostPosted: Mon Feb 09 15 12:35 am    Post subject: Reply with quote

If you were to use new HR steel plate, a 7" 40 grit flap disc will indeed get you down to fresh metal, past the mill scale. A 4'1/2' disc and grinder maybe not. the 4 1/2" would require a bit more elbow grease than one would probably want to use.You would need to use a brand new disc and grind at an angle rather than laying the disc parallel which would only polish the scale. If as mentioned, you are using weather seasoned ( aka rusted, pitted), the mill scale has somewhat become one with the steel. A blast would then be required. I mention this because I have located drops the size you are looking for in good shape of HR a-36 plate at my salvage yard. Never have I found any decent CR steel as scrap. And I agree with the others here, a wire wheel cup is going to get you nowhere on this. So your options are...Cold rolled (CR), blast or possibly what I offered up. This has been my experience fwiw and what I offer up. Lastly, if you decide to go with the CR steel and are unable to find a drop that will work, rather than purchasing what would probably be the smallest plate available, a 4' x 8', I might suggest a specialty steel vendor such as Discount Steel. They will custom cut you any size you need. Not as cheap per/LB as a full off the shelf plate but you won't be looking at what to do with the remaining 26-28 sq ft or so. A quick check using Discount Steel purchase calculator show an 18" x 24" x 3/8" thk HR P&O ( pickled and oiled) shear cut can be purchased for $45 plus ship. The P&O eliminates the scale. Their are other vendors out there, worth a thought perhaps.
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enduro
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PostPosted: Wed Feb 11 15 3:34 am    Post subject: Reply with quote

If there's a local machine shop that has a Blanchard grinder, they should be able to grind it top and bottom to a clean up in a short amount of time. May be worth the hourly rate...or possibly trade for some tasty treats.
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