I recently tried to paint some naked alu and then a steel alloy (amplifier) chassis that was already painted white by the manufacturer .The painting was done by an auto shop worker using spray gun and some blue metallic paint left over from my car.
However in both cases this paint process chips off very easily and is practically useless.
What is the correct way to do this and what preparation/chemicals are necessary for a nice glossy finish?
However in both cases this paint process chips off very easily and is practically useless.
What is the correct way to do this and what preparation/chemicals are necessary for a nice glossy finish?
I doubt epoxy primer is suitable. You need an acid based etching primer.
If the galvanised surface has been primed properly then just a 'key' of the original paint (800 grit wet & dry paper used wet) will be sufficient, no primer needed. If it has been painted by an amateur in the past it may need cleaning down to metal and etch primer applying as you would in the case of the aluminium enclosure.
Any new/bare metal would need keying as above.
If the galvanised surface has been primed properly then just a 'key' of the original paint (800 grit wet & dry paper used wet) will be sufficient, no primer needed. If it has been painted by an amateur in the past it may need cleaning down to metal and etch primer applying as you would in the case of the aluminium enclosure.
Any new/bare metal would need keying as above.
Depends on the quality of the epoxy primer used.
As a boat guy i've used a lot of epoxy primer on metal and aluminium parts. If done properly it withstands much more than the case of an amplifier. Steel and aluminium keels of sailing yachts encounter serious vibration and bending forces.
The trick is to get it totally clean, sand or grit blasting is preferred.
As a boat guy i've used a lot of epoxy primer on metal and aluminium parts. If done properly it withstands much more than the case of an amplifier. Steel and aluminium keels of sailing yachts encounter serious vibration and bending forces.
The trick is to get it totally clean, sand or grit blasting is preferred.
The only way to ensure a quality painted finish on aluminum is to acid etch the surface, dye the metal and then anodize to stop further corrosion.
There are many companies that offer anodizing, however since you are probably only doing a chassis the upstart costs can be high +- $200. I use a company in San Jose CA which charges about $50 for a run.
The finish quality is great. See:
http://www.diyaudio.com/forums/attachment.php?s=&postid=867524&stamp=1142180289
Let me know if you would like for inforamation
There are many companies that offer anodizing, however since you are probably only doing a chassis the upstart costs can be high +- $200. I use a company in San Jose CA which charges about $50 for a run.
The finish quality is great. See:
http://www.diyaudio.com/forums/attachment.php?s=&postid=867524&stamp=1142180289
Let me know if you would like for inforamation
It is not necessary to anodize the aluminum in this case, and I doubt if it is even worth the effort ...ever. If it was necessary, then all aluminum products everywhere would be anodized first proir to painting....and they're not.
However, if it suddenly becomes necessary for all alumnm to be treated that way , please let me know first, so I can open an Anodizing business........
A nice sanding down to bare metal...or at least down to the old primer is fine. Etch bare metal with "aluminum conditioner" (that's really just a weak acid). Wear gloves and eye protection!!!!!!!!!!!
Have your painter friend put a coat of epoxy primer on it. You should put the rest of the paint over the epoxy asap, because it adheres best, when the epoxy is still "fresh".
I have used this common bodyshop primer with perfect sucsess:
http://www.ppg.com/refinishftpsite/docs/P-196_DPLF_Epoxy_Primer.pdf
=RR=
BTW Neil...nice work, beautiful !!
However, if it suddenly becomes necessary for all alumnm to be treated that way , please let me know first, so I can open an Anodizing business........
A nice sanding down to bare metal...or at least down to the old primer is fine. Etch bare metal with "aluminum conditioner" (that's really just a weak acid). Wear gloves and eye protection!!!!!!!!!!!
Have your painter friend put a coat of epoxy primer on it. You should put the rest of the paint over the epoxy asap, because it adheres best, when the epoxy is still "fresh".
I have used this common bodyshop primer with perfect sucsess:
http://www.ppg.com/refinishftpsite/docs/P-196_DPLF_Epoxy_Primer.pdf
=RR=
BTW Neil...nice work, beautiful !!
An autobody /auto paint supply store will carry an already diluted - ready to go solution. Or a well stocked general paint store.
If you do go to a chemical supply, you won't need much. It's possible they sell pre-dilluted stuff. I'm not sure , I think it's 10-20% acid ---->to the water, brushed on, kept wet (keep re-brushing) for about 5 minutes, rinsed thoroughly. You will know it has been etched when the water no longer "beads" on the metal.
Always pour acid into water...not the other way around.
Why?? not sure, I assume that having full strength acid out in the open is just too dangerous, but when adding acid to the water, it is instantly dilluted, and therefore safer to work around.
=RR=
If you do go to a chemical supply, you won't need much. It's possible they sell pre-dilluted stuff. I'm not sure , I think it's 10-20% acid ---->to the water, brushed on, kept wet (keep re-brushing) for about 5 minutes, rinsed thoroughly. You will know it has been etched when the water no longer "beads" on the metal.
Always pour acid into water...not the other way around.
Why?? not sure, I assume that having full strength acid out in the open is just too dangerous, but when adding acid to the water, it is instantly dilluted, and therefore safer to work around.
=RR=
redrabbit said:
"Always pour acid into water, as the reverse could cause a cloud of dangerous fumes to immediately bubble up"
Quoted from a printmaking lab on using nitric acid for etching zinc plates.
I suppose if you are clumsy and pour the water into the acid to quickly it could splash out and start etching your flesh as well.
Stan
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.