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Originally Posted by JTW37
I have a couple of questions...
1. When you Media Blast, is it necessary to dip or spray with phosphate?
(The way I understand it is, it's to give the powder something to bite into.)
2. When you clean a part, do you need to submerse it in the solution and what are you using to clean?
(So far I have used Simple Green and only sprayed and scrubbed with a brush and then rinse in clean water.)
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Let me add a few things to the proper & correct answers you have already received on the above questions..
On "media blasting", depending on what you are using, you may or may not be adding "tooth" to the metal, which does aid the paint, powdercoating, etc., to stick.. I blast with "real #4 Blasting Sand" (get back, everyone thinks I breathe silicosis.. I assume you have a second brain cell that knows to use the proper safety equipment/respirator, etc.) that has been "recycled" (reused) three or four times and produces a "satin finish", as well as the necessary "tooth" on the metal.. plastic beads, soda blasting, etc. do not add "tooth".. nor do they clean the rust out of any pits in the metal.
Once the part is in "bare metal", and depending on what the humidity levels are where you live, you may have anywhere from a couple of minutes to months before surface rust starts to form (coastal areas have seconds!!) so you WILL need to powdercoat the part immediately.
On the cleaning.. I've heard "Simple Green" is good, a number of electroplaters use Dawn Diswashing Liquid to clean their parts prior to plating, it is a good grease cutter as well.. others use a product called "SP Degreaser" (Caswell sells this-- it's good stuff!).. parts are cleaned in a 140-200 degree bath of this degreaser, and it cuts the grease!! I believe it is "caustic based" so heavy rubber gloves, eye/face protection are required, but the stuff is safe enough to be diluted and poured down a household drain (follow instructions, local EPA laws, etc. usual "CYA" stuff)
The Most Important thing is... DO NOT Sandblast a greasy or tar coated part, ever!! The air pressure from blasting will drive the grease/tar into the "pores" of the metal and this WILL cause you problems later.. So, the strongest advise I can offer is to clean/degrease your parts before you do any blasting (some platers/powdercoaters, myself included, even degrease the parts AFTER blasting, as well!!), clean part again, to remove any possible residue of the SP Degreaser (if you opt to use it)... it should go without saying, but NEVER touch a freshly blasted bare metal part with your oily hands!! Wear Nitrile Gloves!
I hope the above adds a bit of useful information to your mental metal prep files and is of some help to you.