Tim Attwood nous apporta ses lumieres en ce 2007/08/29 17:40:
>> Hmm, electroplating with Ni in a Watts bath needs a temperature of about
>> 60-70ºC... I don't know about Cr. That would probably melt polystyrene,
>> never mind dissolve. I agree about the orange juice though. :)
> 
> I saw a guy being interviewed on a car show who chromes
> restored plastic, even glued together bits. He paints it with
> some sort of expensive silver paint, then electro-plates with
> copper, then nickel, then chrome.  I think the copper may
> help dissipate the heat. 
> 
> 
The copper holds well on the silver paint, but nether the nickel nor the chrome 
will. The copper plating is to thin to help protect from the heat.
Then the nickel makes an exellent bond with the copper, while the chrome will 
peel from it.
Then the chrome will perfectly fuse onto the nickel. Also, the nickel makes an 
harder, more resilient, substrate.
You go from "soft" (the plastic) to prety hard (nickel then chrome).

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you downloaded and printed the 
Renderman Interface documentation, so you'd have a little light reading to take 
on holiday.
Alex McLeod a.k.a. Giant Robot Messiah

Post a reply to this message

Alain <ele### [at] netscapenet> wrote:
> The copper holds well on the silver paint, but nether the nickel nor the chrome
> will. The copper plating is to thin to help protect from the heat.
Quite the opposite, probably - Cu is an excellent thermal conductor.

> Then the nickel makes an exellent bond with the copper, while the chrome will
> peel from it.
> Then the chrome will perfectly fuse onto the nickel. Also, the nickel makes an
> harder, more resilient, substrate.
Having had a quick peek at the binary phase diagrams, this seems to be
because Cr is soluble in Ni at low concentrations, and both Cu and Ni are
soluble in each other to a small degree, whereas Cr and Cu appear totally
immiscible.

The silver paint is probably just to give the substrate all-over electrical
conductivity so it can act as an electrode during the plating process.

Anyway, that's not how I made my styrofoam blob; I used a magic chrome corn
kernel in a giant popcorn maker. ;-)

Post a reply to this message

Bill Pragnell nous apporta ses lumieres en ce 2007/08/30 05:09:
> Alain <ele### [at] netscapenet> wrote:
>> The copper holds well on the silver paint, but nether the nickel nor the chrome
>> will. The copper plating is to thin to help protect from the heat.
> Quite the opposite, probably - Cu is an excellent thermal conductor.
Sure is. And, for exactly that reason, it won't protect the plastic from the 
heat, as in the plating vat, heat comes from all around. Cu will transmit that 
heat quite effeciently to the plastic!
> 
>> Then the nickel makes an exellent bond with the copper, while the chrome will
>> peel from it.
>> Then the chrome will perfectly fuse onto the nickel. Also, the nickel makes an
>> harder, more resilient, substrate.
> Having had a quick peek at the binary phase diagrams, this seems to be
> because Cr is soluble in Ni at low concentrations, and both Cu and Ni are
> soluble in each other to a small degree, whereas Cr and Cu appear totally
> immiscible.
So Ni will bont to Cu, then Cr will bond to Ni, but Cr will not bond to Cu, nor 
will it bond to Ag.
> 
> The silver paint is probably just to give the substrate all-over electrical
> conductivity so it can act as an electrode during the plating process.
Only plausible explanation. The paint's cost comes fron the silver dust it contains.
> 
> Anyway, that's not how I made my styrofoam blob; I used a magic chrome corn
> kernel in a giant popcorn maker. ;-)
> 


-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when your personal correspondence to 
friends starts out with #Dear Linda =
Ken Tyler

Post a reply to this message

>>> The copper holds well on the silver paint, but nether the nickel nor the 
>>> chrome
>>> will. The copper plating is to thin to help protect from the heat.
>> Quite the opposite, probably - Cu is an excellent thermal conductor.
> Sure is. And, for exactly that reason, it won't protect the plastic from 
> the heat, as in the plating vat, heat comes from all around. Cu will 
> transmit that heat quite effeciently to the plastic!

I was thinking about the heat, they guy did say that other platers
were trying to do plastic but wern't getting as good of results.
He probably didn't share his "secret".  I'd guess that he uses a
heatsink on the electrodes, that would transfer the heat up off
the copper layer and out of the bath. Silver is also a better heat
conductor than copper, which may be why he was using
paint with silver in it instead of just iron or copper in the paint.

Post a reply to this message