Now, why is it bad? What makes chrome plating bad? I want to break this into two different sections.
This idea is basic. The plating process actually weakens the parts. This article on bikeguide is where I first read about this, and I would like to link it here.
"Tensile strength is the pulling of a material until it tears apart. The higher the tensile strength, the more susceptible it is to embrittlement. When you chrome a part, hydrogen is soaked into the material as it is plated, the plating then holds it in. Once inside it will spread to all areas, where it is relatively harmless. When stress is applied, the hydrogen re-distributes itself, concentrating on the point of stress. Think of it as trying to escape, and its only way out, is a crack."
That's all well and good, but I know what some of you are thinking. Some of you are thinking that your rims aren't 4130 CrMo, they're Aluminum! So they're safe! Right? Well....
This problem will happen on anything that is plated in chrome (or any other material). A common principle is that when metal heats up, it expands. And as it cools, it contracts. It's not just metal that does that, either. That is why when going over a large bridge, you will see what looks like a bunch of little fingers every 50 feet or so. Those were not the sections that the bridge was built in, those are expansion joints - so that when the metals expand and contract the bridge does not buckle - causing a catastrophic failure.
That same principle applies to your frame and wheels. Nowadays, bmx only really uses chrome on wheels with brakes. There isn't much of it floating around elsewhere. So, the problem is that when the rim heats up or cools down, so does the chromium that is used in the plating process.
There's a catch though. Different metals tend to expand and contract at different rates. Thus, when the rim heats up - the aluminum will expand at a different rate than the chrome plating. When this happens, the chrome plating needs to expand or contract to keep up with the aluminum. Unlike those bridges I talked about, your rims do not have expansion joints. Therefore, the chrome buckles, causing a failure (a crack).
So keep your bike out of the oven then, right? Well, if you have a chrome rim for brakes, then chances are you...well, have brakes. And brakes stop your bike using an anti-gravitron device. No, not actually, they use friction, which produces a sudden heat transfer. Remember, heat is not the enemy - the sudden heat transfer is. The chrome plating does not have enough time to catch up to the aluminum, and will crack.
This is why rims crack and bubble. Cleaning them will do next to nothing as far as cracking and bubbling from thermal expansion goes. Cleaning them will help against corrosion, but cannot fight physics.
This will also happen without brakes, too. The same principal of thermal expansion applies to frames, forks, etc. Heat transfer happens all over your bike.
Here's a problem though. Some of you may know what my bike looks like, and are thinking "well, Pickles, you run a chrome plated rim though! What gives?" First of all, if you actually thought "What gives?", then please, please come to the current era. Second of all, I know that. For me, it's worth it. I run a chrome rim for functional purposes - my brakes. If it were a painted rim, the paint would wear out even faster than the chrome plating will.
There's a nice bonus to my rim as well - I run a GSport Ribcage. GSport warranties against cracking/bubbling. This surprises me, considering that's not something that is their fault, but I don't argue. They stand behind their Ratchet hub with a lifetime warranty. The confidence they have in their products is impressive.
So, to me, a chrome plated rim is worth it. It will crack and bubble, but I would rather have that happen than to deal with a painted rim with brakes.
Question: How do you remove chrome?
Answer: Professionally. I would tell you how to do it, but it's not worth it. The process produces hazardous materials, and the chemicals used are dangerous. You would have to bring it into a professional to have that done. Please, PLEASE do not try to do it yourself.
If you have any questions about anything written in the article, leave it in the comments and I will get to it as soon as I see it.