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Topic: Chrome plating  (Read 12999 times)

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Chrome plating
« on: April 19, 2004, 05:36:54 PM »
Earlier, plating was mentioned and that peaked my interest. The best way I learn is by practical application, so I started reading up on it with the end result being able to plate various sections of my engine in chrome! Got a couple questions though:

As I understand it, a more reactive metal will displace a less reactive metal so long as that less reactive metal is part of some compound. Lets take iron (engine parts) as our more reactive metal. I found some lists of reactivity for metals, and I couldn't find chromium on there, so I'm basing this on the assumption that chromium is less reactive than iron. If I'm wrong, there's no point to all of this. So, if you have more reactive metal plus less reactive metal compound, you add heat to make the reaction happen if both reactants are solid. If the less reactive metal/compound is in a solution, you just dump in the more reactive metal and wait a week or so.

I looked up chromium on an elements page, and it said that chromium is NOT soluble in water. Thats fine, it needs to be part of a compound anyway. So which would work, a chromium salt, or chromium oxide? And if a salt works better, what should I combine chromium with to make it as easy as possible for iron to displace it? I want the less reactive compound to be aqueous, because I want to store it in a big bucket, and toss parts of my intake, bolts, and such in there. So still assuming that chromium is less reactive than iron, once the iron is sitting in the solution, the iron and chromium are going to trade places, and I'll have a piece of iron with a chromium shell around it, since the whole chunk isn't going to get displaced. Do you guys see any holes in this logic?

Offline gregpawin

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Re:Chrome plating
« Reply #1 on: April 19, 2004, 06:09:23 PM »
Well, I hope you're not thinking you can simply apply some electricity with some chromium in solution nearby.  As I recall, there are often demonstrations for chemistry classes showing how a metal in solution plates another metal with some electrochemistry.  However, the chromium plating you and I have seen on bumpers and such are much different processes, which require the use of some very toxic gases.  Demonstrations of electroplating usually end up with spoons or such covered in a crusty, grainy solid... not a smooth shiny surface.
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Re:Chrome plating
« Reply #2 on: April 19, 2004, 06:19:25 PM »
So THATs why its so expensive! Well even with a grainy rough surface, it would be sandable to shiny smooth? Or would that just tear up the thin coating I had?

So you're saying my logic is good and it'd work? Didn't know you'd need electricity, because I'm electrolysis stupid. From examples I looked at for other reactants, they just let the stuff sit in the solution for a while and it did its thing all by itself. How do you know how much electricity to use anyway? I assume a car battery is a bad idea...

Offline Donaldson Tan

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Re:Chrome plating
« Reply #3 on: April 20, 2004, 02:48:22 AM »
Heard of electroplating? Industrial electroplating involves toxic metal cyanide solution as cyanide makes good chelating agents to ensure smooth & uniform plating

"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006


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Re:Chrome plating
« Reply #4 on: April 20, 2004, 11:41:50 AM »
Electroplating sounds familiar, but I have no idea how it works. Is there a safe way of electroplating something that I can do at home? Just to demonstrate the concept (I have to try everything), is there something simple I could try doing?

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