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  1. #1
    Join Date
    Oct 2009
    Reno, NV

    Default Painting...Remove mill scale or not??

    I am building a cart for my new Miller 211 and am going to paint it when I am done. I have always media blasted anything I made (well, welded) and painted. Using fairly aggressive media removes all the mill scale pretty easy and the paint seems to go on nicely and then stick pretty well. Problem is, some parts that I have made the cart out of have mill scale and some not. Mostly I have only removed it where I wanted a good clean weld.

    Question is....Now that I have some parts with scale and some not, do I have to get the scale off in order to get paint to stick well? I will, of course get any oil and etc off, but I have heard of some people just painting right over the scale. I tend to think that I have to get it all off of there. What results/experience have any of you had with painint over mill scale?

    By the way, it looks like the Rustoleum Safety Blue is the best match for my Miller 211according to the checking I have done....Is this good or is there something better..(Cheap, easy to find, etc)? I just won't pay the HIGH prices Miller wants for THEIR paint.
    Don J
    Reno, NV

    Never pick a fight with an old guy. Old guys are too smart to fight and get hurt. They'll just kill you and get it over with.

  2. #2
    Join Date
    Oct 2007
    Cave Creek Az


    Welding cart, just paint it. Dining room table, remove it or prime and block sand and paint it.

  3. #3
    Join Date
    Mar 2011
    st-eustache qc.canada

    Default wash and paint

    since scale is harder to remove than most paint why bother, i have been painting machinery with cheap machinery enamel for 20 years, right over scale, most of the time without primer and (maybe i am lucky) never had adherence problems.

    good luck whatever you decide, post pics ;o)

  4. #4
    Join Date
    Dec 2008


    The safety blue is very close to Miller's current shade of blue. On a few projects I've done I've used that as the first 2 coats and used Miller's blue for the final coat. When spraying on the final coat I haven't noticed much difference between the two.
    As far as the mill scale, this is a project for the shop, not a museum....
    Miller Syncrowave 200
    Homemade Water Cooler
    130XP MIG
    Spectrum 375
    60 year old Logan Lathe
    Select Machine and Tool Mill
    More stuff than I can keep track of..

  5. #5
    Join Date
    Dec 2009
    Northern California


    If you are looking for a professional appearing, super smooth finish, then the scale will have to be knocked down. But if you don't mind a slightly industrial finish, then just clean it up and spray it!

    I've often cleaned off bare metal projects after blasting, wiped them down and then hung them up and heated the materials with a propane torch. The moisture and oils are evaporated off and then I will lightly spray a tack coat then let sit a while before going back and covering the entire project.

    Doing the paint to metal straight without primer after heating the metal and burning off the oils and moisture gets a good bond that lasts a long time!

  6. #6
    Join Date
    Jul 2011


    Mill scale varies in thickness. It is brittle so if there has been any cold work after mill forming, the mill scale will crack and provide attack points for corrosion.

    I've pulled mill scale off of thin tube using phosphoric acid. Fast and leaves a fine profile for painting.

    My generator had peeling paint because its case was rolled from 3/16" HR sheet. I stripped off the paint, then used phosphoric acid to remove the remaining mill scale before priming and painting.

  7. #7
    Join Date
    Mar 2010


    Right Stuff rust converter is terrific and we've been using it for years over scale and light rust. We treat everything we want to stay pretty.

    We've left treated parts sitting in our sometimes humid garage (South Carolina) for weeks with no corrosion.

    We sand, prime and paint afterward.

  8. #8
    Join Date
    Dec 2011

    Default just paint it

    i understand the need for everything to match but a shiny black compliments miller blue quite well just a suggestion, that said, i have a lincoln 225 that i inherited and now that i know rustoleum safety blue id that close i think i'm gonna paint it to match my big blue lol

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