Christiaan

I have a 4130 frame with a rounded dent about a centimetre in diameter. I've been advised by a frame builder that it's a filler job.

I also want to get the frame powder coated by Armourtex, which includes shot blasting and heating (180-200ºC).

So what's the best filler to use in this situation?

Iowegian

I'd ask your powder coater for recommendations. My understanding is that the powder will only adhere to metal before baking so the filler will need to have some metal content unless there is a special filler used for power coating. You can put any kind of brazing material in there and it should work but it will be more work to apply and finish.

jimc101

If you need a dent fixed, why not get the frame builder who recomended it to do it?

How long has it been dented, as it's Steel, if it has been there for a long time, can it be lived with?

If not, how about trying places like Condor, Brixton Cycles, Bike Fix or any other bike shop for for advise on who locally can do the repair.

AEO

if it wasn't being powder coated, I would just use bondo on it.

BCRider

If you get it actually powder coated the filler will need to be a conductive metal such as solder. Any regular autobody fillers or similar won't respond the the electric charging and make the powder stick to the frame. If it's a small dent or two that are quite shallow the amount of weight you'll add is negligable. You'll need to totally sand out the area and then use plumber's solder and flux along with a propane torch. Build the area up higher than you need and then file and sand away the excess to blend the dents.

If you want to just use Bondo or similar then you would have to switch the plan from powder coating to regular painting.

Or perhaps given that powder coating is becoming so mainstream they may have a metal particle style of filler that is conductive. Try asking the coater.

Anthropy

I found this stuff while surfing. Says it is good before power coating

Hi-Temp Lab-metal must be baked at 425 deg F for an hour and then is good up to 1000 deg F.

Then there is Lab Metal which is good up to 425 deg F and looks like it requires no heat curing. 51% atomized aluminum powder so it must be conductive.

Fastenal carries it Lab-Metal 20oz tube for $27.19


Tom

ultraman6970

Ask the painter what he uses or what he has used. THere are several potty's moving around but you need one in specific, wonder why not let the painter deal with the dent? for sure he has the material needed for the job, ask him how much extra for fixing that imperfection.

As for bondo. thats the worse thing ever, the problem with bondo in general is that never BONDS 100% with the metal, so when the metal expands or contracts bondo just starts cranking. For regular wet type of paint you need a potty made of polyester, it is like plastic, doesnt crack, it bonds 1000000% to the metal and doesnt crack with changes of temperature as bondo does.

Christiaan

Thanks for the advice guys. I asked Duncan at Armourtex and he basically said none of the fillers on the market stand up to the preparation process (of heat and blasting). He recommended having it brazed and said they partner with a company that can do it for a tenner or so, so that's cool.

So, I was wondering, if they braze it with silver will it look similar to the bare steel? Because I was toying with going for a clear finish.

jimc101

A clear coat on raw steel will look nasty, and show up all the welds, and discolourations & repairs as this will not have been finished for this when built.

Would suggest getting a grey coat it you want to give the impresson on raw steel or pick a colour they have

fietsbob

Colo(u)r : AUDI/Porsche silver metallic ..

BCRider

If you wanted a clear finish I'd suggest playing with some coarse swirl marks left by a coarse metal prep pad. An overlapping series of arced "scuffs" left by such a prep disc in a skillfully held angle sander could result in a nice sort of fish scale look that would really make a clear coated steel frame pop nicely.

Silver brazing still doesn't look like steel. It has a bit of a bronze cast to the metal colour. And regular brazing is typically a brass alloy so of course it looks like what it is, brass. If you do the prep yourself using the overlapping scuffing pattern idea I think you could get away with using the plumber's solder and just use a VERY light touch with the metal prep disc when going over the actual patches. And it would likely be you that did that part since the scuff pattern would be the very last thing done before either a paint clear coat or a clear powder was applied.

Be aware that clear coats can really mess up a "brushed" finish of this sort. You WILL want to first of all practice on something free such as a few bits of electrical conduit to develop your skill to get a nice look with the scuff patterns. At that point and with a couple or three tubes you'd want to try one with your clear coat choice and see the outcome. Some clear coats really make a brushed finish like this sparkle and others can make it all turn a dull grey. The factor that affects this is the refraction index of the coating. And there's no way to tell other than by experience. Either your direct experience from trying a bit or some serious assurances by the painter or coater that has done the same sort of work in the past with that product.

If it works the look would be amazing so if you don't mind the extra work it would be worth doing.

1saxman

Thanks for the tip on Lab Metal. I need something like that for another project, a 1950 Thimbledrome tether car with aluminum body. I'm sure I'll find plenty of other uses for it too.

ETA: After seeing the Lab Metal site where it is specifically recommended for powder coating, I'd say it would be the best way to go on the bike frame, assuming an opaque coating.

Dangerboy6969

https://www.bikeforums.net/archive/in.../t-720479.html

Dangerboy6969

https://www.bikeforums.net/archive/in.../t-720479.html I used this and turned out good powder coating my fender.

rpenmanparker 

Bare metal look is cool when protected by a clear coat. I wouldn't worry about the silver not looking right. That is the whole point of the bare metal look. The imperfections are what makes the look desirable. Perhaps you have never seen what a brazed frame looks like before priming. It ain't pretty, but that is the whole point. Don't forget you need to bring in color with your saddle, cable outers, bar tape, and rims or tires. That is how you dress up the look.

Grand Bois

It's interesting that it states on the the site that Lab Metal is non-conductive.

Matariki

The problem with just filling a dent is that frequently the tube is slightly oval at that point. To fix this I use fitted blocks to roll out dents as much as possible. This returns the tube to round as well as reduces the dent. Depending on the size of the dent I will use brazing rod, silver solder, or for small dents, auto body lead. The latter is silvery like steel and hard to detect when everything is polished up.

Good luck.

Fidelista

Clear powder coat over bare steel. It's a lot of work by hand to prepare for powder coating.
Click on the pic for a larger image.