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  • Another sandblasting/prep question

    Ok, I've searched and read, and I have a question about blasting. Basically, I'll likely be powdercoating mostly engine and automotive parts, which are often fairly dirty. Now, I see a lot of different types of blasting media, and I just want to know what is going to be the best for me. I've heard reccomendations of aluminum oxide, glass beads, silica sand, and even baking soda. Which one is right for my applications? And if one is best for smoothing out a surface (such as cast aluminum, or uncoated mild steel), I'd like to know that too. A compromise between the two would be ideal, if possible.

  • #2
    okely dokely..... for basic steel prep you can't beat a good aluminum oxide. The trade names for this are many but "black beauty" and "00-grit" come to mind. This is good for removing heavy scale and rust, smoothing out major surface scratches and the like. I use this on my intakes,hood hinges,headers,etc. The stuff that gets really nasty and needs to be worked on from the most basic metal. Glass bead is good for things from the machine shop in "cleaning it up" after a basic process of honing, decking, etc. I've also found it useful to prepare the surface for removing minor casting flash,small imperfections,etc. While not a profile creator like the black oxide...it's a good all around general purpose blasting media. Next we have walnut shells,plastic media and the like. Good for removing paint and past coatings of the liquid variety, but not anything to write home about on the prep area for powder coating. I'd have to say that would be best used in metal interior parts like kick panels and such for older cars. Removes the pain and doesn't chew away at that thin gauge metal from yesteryear. After that the next grade is baking soda. While it's not really a fantastic blasting media, it has it's purpose. Delicate parts requiring very little to no rough treatment is where this product excels. Let's say vintage white metal script and ornametal pieces on a car is where this belongs in your applications?

    I've touched on this in the Tips and Tricks thread a bit...but basically that's about the jist of it. I know there's millions of other media types and thier purposes out there...but maybe somewhere in there you found the basics to get you started as far as surface prep for powder coating is concerned. Hope that helped a wee bit.....Russ

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    • #3
      Great, exactly the info I was looking for. thanks.

      One more question: If I'm using a translucent powder on, for example, a plain mild steel pipe, i should use a chrome powder first for the shine under the translucent powder, right? What if the pipe is polished stainless, do I still need to apply the chrome base powder, or can I just use the translucent powder over the stainless?

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      • #4
        In my past experience..... a clear over a sandblasted piece of metal just looks like shiny sandblast. Gloss-frost if you will. I'd most definately put a base coat of a reflective coating underneath and then a clear coat on top for protection's sake (especially the invironment you're going to use it in. Car parts are never treated kindly unless it's a trailer queen). A word to the wise before I continue on with this subject..... It's best if you are doing this same process to a tire rim to always put a clear coat on. Due to the fact that brake dust when mixed with water or even humidity turns acidic, your coating will most assuredly get hazy looking and such, no matter the colour. It's most noticeable on silver/red/high pigmentation colours as they tend to "fog" first. Clear has no pigmentation to impede the bond of the coating, therefore it's stronger. 'nuff said.

        Anyhoo..... I'd put a reflective coating on as my base and then a clear,yes. If a white basecoat then you may "augment" it's appearance by coating with a tinted clear. What one may come up with is a bright honey shade, perhaps a neon looking red or if you have a clear with metallic or prismatic additive.....it will appear "suspended" on your part. Ergo...really bouce out at ya. Nice when done properly.
        As for coating on bare stainless with a clear. Hmmmm...Stainless by nature tends to discolor when heated. It's just one of those funny characteristics of the metal and it's alloy contents. You may be able to buff it to a high-gloss with the Caswell compounds(green for stainless if memory serves) and then remove any debris with a wipedown and HcL (hydrochloric acid) wash to bleach the colour out, but like I said before....for automotive application it's usually best to have a two-coat process. If nothing else....for durability sake alone. Stone chips, the errant wrench or possibly any other element unforseen by you. If you don't mind the "non-chrome" look I'd go with the clear on top of bare substrate. Be forewarned though.... I bet even money that it will slightly "yellow" and have a titanium sort of look to it.

        Hope that helps bud......post some pictures in this column to show us how it all came out if you can,k?.....Russ

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        • #5
          Just to hit back on the blasting question, i'd recommend using a coarse media such as aluminum oxide or black magnum, which is dirt cheap. Stay away from silica sand, its bad bad stuff unless used properly. In your case you're doing engine componests which are probally either beefy cast aluminum or beefy cast iron, so a more coarse abrasive wont hurt it like it would a thinner sheet metal. I too do a lot of automotive parts and run 3 cabinets, one with walnut shell/plasti-grit for paint removal, one with glass bead/alum oxide mix for lighter more delicate things, and one with black magnum for heavy blasting on intake manifolds etc. Good luck and feel free to ask questions. We like helping!

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          • #6
            how is silica sand bad stuff?

            you said that if used improperly it is bad stuff. I need to strip the paint off a motorcycle frame & was going to use silica sand. Do you recommend another media?


            nutty
            SouthWest Powderworx
            Tyler Nutter
            5054803934
            www.swpowder.com
            myspace/swpowder
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            • #7
              I do not recommend silica sand. Loom around the local hardware stores for something called black beauty/black magnum/coal slag. Its similiar to silica with a very low content of crystaline silica. Your lungs will thank you. Its dirt cheap, just like play sand aswell. Good luck.

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