Metal finishing Q&As since 1989
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Metal and plastic sanding and painting
Q. I am in the process of rebuilding an old dirt bike of mine for a school project. I am planning on tearing the whole thing down to the frame. I want to sand and paint the frame. I also plan on painting the engine assembly, the plastic fenders and the plastic fuel tank. I am very unfamiliar with metal sanding and plastic sanding. I do not know which primers and paints to use for the final finish. I would like any help at all because I have no idea what it takes to do this.
Thank you for your time, sincerely,
- Pleasant Grove, Utah
2003
Dave,
Re your bike and painting plastics ... ah, plastics are like metals in that there are a lot of them, all with different characteristics.
I was told that another do-it-your-self(er)'s bike had Polypropylene fenders. And those, like Polyethylene, are a S.O.B. when it comes to painting.... but in retrospect I just wonder WHY the manufacturers used PP and not ABS which is a tougher material, cheaper and can be easily painted.
If your fenders (and the fuel tank which would definitely not be made of ABS) are PP or Pe, then you haven't got much hope in attaining a good bond. l) Clean off any oil 2) lightly sand ... to remove the oxidized finish which occurs {very quickly) with those plastics and to give a larger surface area for the paint to hopefully adhere to 3) use a flexible paint of some sorts, not a hard enamel.
For the metal components, ie. frame, etc ... any good paint supply house will advise you ... and you can get a good finish using a spray can.
Safe riding !
Freeman Newton [deceased]
R.I.P. old friend (It is our sad duty to
advise that Freeman passed away 4/21/12)
Q. For proper adherence of paint to the polypropylene surface what primer to be used? and which paint to be used along with its additives? As bidke's side fenders are exposed to the sun light, how to maintain its color and gloss?
Thanks for your time,
Dinesh Goelpipes and profiles - New Delhi, INDIA
2004
A. There may or may not be a way to get good enough adhesion on these particular plastic components, but these pages include many recommendations for Krylon Fusion [on eBay or Amazon] paint.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. I have a fabrication facility, and like to give a lasting finish to the plastic components being used as corners and beadings, etc... by painting on to it. it is mostly done to match the base product color (if it is a corner then match the color with the frame's color). mostly the color matching stuff is ok but the lasting part is week as it peels off. can you suggest a best procedure or any paint that adheres to plastic surfaces.
thanks in advance
employee - safat, Kuwait
April 15, 2009
A. Hi, Ayjaz. There are thousands of different plastics. You would have to find out what kind of plastic you are painting if you want to receive exacting advice. But in addition to the primers mentioned here, thread 14173 talks about other possible primers, and flame prep and dyne testing. Good luck!
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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