Author Topic: Filler for powdercoat  (Read 352 times)

Filler for powdercoat
« on: February 08, 2019, 06:48:26 pm »
This is a new one on me.  I bought a rather tired-looking (but perfectly straight)  frame and took it off to be powdercoated.  The powdercoaters have blasted it clean but say there is some filler under the paint (covering small dings, presumably) and this will leave a mark if the frame is powdercoated. 

Apparently some fillers can take the 200 deg C temperature used to cure the powder and also have good conductivity to allow the powder to stick.  Any ideas which?  I have four options:

1. Sand out the existing filler and use something more suitable
2. Get them to blast it out and coat it, leaving the dents as they are
3. Fill it with normal body filler and do a rattle can job (will have to wait until much warmer weather)
4. Get it enamelled instead - not economic, as it's a gift for someone

EDIT: some alloy wheel filler (not expensive) claims to do the trick.  Very high metal content and resistant to powdercoat temperatures.  Makes sense: the professionals fill kerbed wheels all the time before powdercoating them (not the guys who do it in a van, the big workshop-based outfits like BJV Engineering, who are excellent by the way if you're within reach of Chenies/Hemel Hempstead).
Never tell me the odds.


Torslanda

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Re: Filler for powdercoat
« Reply #2 on: February 11, 2019, 09:07:56 pm »
Wurth also sell a high temperature filler which gets good results in a powder coat.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Re: Filler for powdercoat
« Reply #3 on: February 12, 2019, 02:32:41 pm »
Turned out to be silver solder rather than filler.  Sloppy framebuilding, Holdsworth must have used dented tubes to avoid scrapping them.  At least, I hope it's not ordinary electrical solder, as that melts at about stoving temperature instead of 650 deg C!

They're going to shove the bare frame through the oven at 180 deg C  just to check it doesn't melt, before applying any powder.
Never tell me the odds.

Re: Filler for powdercoat
« Reply #4 on: February 13, 2019, 01:17:19 pm »
And...it was crappy electrical solder!  Looks as if this will be a rattlecan job for the summer, unless anyone knows a surefire way to remove all traces of solder from the frame (I'm thinking a blowlamp and desoldering braid, but it could be super-laborious).
Never tell me the odds.

jiberjaber

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Re: Filler for powdercoat
« Reply #5 on: February 13, 2019, 01:26:03 pm »
And...it was crappy electrical solder!  Looks as if this will be a rattlecan job for the summer, unless anyone knows a surefire way to remove all traces of solder from the frame (I'm thinking a blowlamp and desoldering braid, but it could be super-laborious).

gental blow lamp to get it flowing, hanging upside down from the dent then flick out with a screwdriver.... (obvs being careful etc)... should reduce the amount of braid you'd have to use.  I think you will still end up with some coating where it has flowed on to the metal.  ???
Regards,

Jason

Re: Filler for powdercoat
« Reply #6 on: February 13, 2019, 01:33:41 pm »
old electrical solder is a eutectic composition and wouldn't be used as a filler. Higher lead content solders have a broad 'mushy' range and in the past were used for 'wiped' soldered joints and as body filler in car repairs.   It is most likely that you have that kind of solder, used in the same way as 'lead loading' would be used in car body repairs.

If you used something other than powder coat to finish your frame, you could leave it be. As it is you have a potentially toxic problem.  The lead loading should just wipe off (eg with a piece of leather) when molten; it needs encouragement to wet onto a steel surface and will soon de-wet unless there is flux present.

cheers

Kim

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Re: Filler for powdercoat
« Reply #7 on: February 13, 2019, 01:44:14 pm »
And...it was crappy electrical solder!  Looks as if this will be a rattlecan job for the summer, unless anyone knows a surefire way to remove all traces of solder from the frame (I'm thinking a blowlamp and desoldering braid, but it could be super-laborious).

Not sure if it'll help, but super-low-temperature solder removal alloys are a thing:

https://www.chipquik.com/store/index.php?cPath=200

The idea being that you dilute the solder with the magic stuff, then it stays molten for *much* longer than usual - primarily helpful for removal of large SMD components that are difficult to keep at soldering temperature without damaging the board.
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