Two pack vs. powdercoating

[samSC1192]

two pack vs powdercoating

hey guys i have a set of 4 mo bora stockies that i got hold of cheap that have gutter rash all over them. my mate is sandblasting them for me this week and im going to have them painted im just wondering what finish would be more durable and what experiences people have had with either of these finishes? I was gunna go the good old spray can job on them but even though they are a cheap wheel i think its worth a bit of extra coin to have them be a little more durable and last for years to come.
i know there is probably heaps of stuff on the net about this it would just be cool to get a couple of opinions

cheers sam.....

[team_v]

powdercoating is said to be more durable as you don't seem to get scratches in it.

However powdercoating needs to be baked and if they are baked above 400 degrees C it will appaarently alter the properties of the aluminium in the wheel and make it more brittle.

[wai]

The curing process for powder coating requires a higher temperature to melt the powder and get it to flow. You might want to check with the wheel manufacturer because many aluminium alloys (many alloy wheels are aluminium alloys) are "solution heat treated" (i.e. during cooling, they are quenched at a particular point to prevent certain alloying elements from precipitating out). If they are heated beyond a point for a prolonged period this can cause these elements to precipitate out effectively reversing any heat treatment. It may well be OK, only it might be worthwhile checking.

[samSC1192]

thanks heaps for the quick input i had no idea about this possible problem ill have a look into it. If it is ok to powder coat is it generally cheaper then painting???

[wai]

Not necessarily.

With a wet system, there is just relatively standard spray equipment and a curing oven to vapourise the solvents.

With a powder coating system, you have to have absolutely dry air as amy moisture can cause the powder delivery to clog and clump on the workpiece. This is done by freezing the air to drop all the moisture out of it. Then you need a much hotter oven (not because of the freezing) to melt and let the powder flow. So it depends on the painting outfit.

Colour then becomes a cost issue as if they do not have the colour you want with powder coating as it could be expensive to get it in just for you. You are more likely to have a auto spray painter have the colour you want as opposed to a powder coating outfit.

Looks like some hunting for you

[gavs]

No freezing in our powdercoat line....

ALso, powdercoat is just as suceptable to scratching but because the surface is softer than paint, it does "give" a little more. The other issues are that most wheel cleaners destroy the lustre and gloss of the powder, powdercoat is "melted" at temps of around 200 degrees C in the production line and if you're hitting the anchors pretty hard, your powdercoat is constantly going to be heat cycling and having any pores in the surface opening up and absorbing brake funk, which you will never get out. You need to do a 3-bath pre-cleaning of the products too, as well as a shot/bead blast and finally a pre-surface treatment.

On top of all this, if you get a generic powdercoat, it will be rubbish on the wheels. To give you an idea, a specially formulated powder that is basically just black, is around $6 a kg. A more specialised, harder suface coating with metal flake is aound $16 a kg.

[kaanage]

"solution heat treated" (i.e. during cooling, they are quenched at a particular point to prevent certain alloying elements from precipitating out). If they are heated beyond a point for a prolonged period this can cause these elements to precipitate out effectively reversing any heat treatment.

Actually, the problem is the cooling process (the quench part). ALL aluminum alloys will precipitate out a major portion of their alloying elements but the issue is how these precipitates are dispersed. With rapid controlled cooling, the precipitates will be very small and evenly dispersed, providing mechanical resistance points between the aluminum grains which normally have very soft boundaries. With slow cooling, the alloying elements tend to migrate together as they precipitate out making them useless chunks of harder metal in the soft aluminum base.

Additionally, even if the aluminum alloy has been properly quenched, many alloys take a long time for the alloying elements to precipitate out so they need to be heated to back up a lower temperature to speed up the precipitation process. Otherwise the fine precipitate particles won't be present and you are back to a soft (but very slowly hardening) aluminum alloy (annealed is the proper term here).

Makes you wonder about 6061 aluminum rotor carriers....

No freezing in our powdercoat line....

Do you filter the air through an airconditioning system (ie freeze out the water remotely) before the powdercoating takes place?

[samSC1192]

i might be better off with the two pack i know a painter that has done a couple of fix ups on my car when i got it and does a really good job for a fair price i might go see him this week and i know he will be able to do the colour since im painting them the colour of the car. i take it easy my my car most of the time so i dont use a huge amount of breaking so heat shouldnt affect the wheels right ? and since i clean my car once or twice a week break dust wouldnt eat in ?