The Mark 2 armor is used to be a metal alloy build up of Stark's designs to test the internal components and computer systems newly created. Why the hell would be chrome that especially since the primer over the alloy was gold? The only reason they even built the Mark 3 is because they needed to add the modifications for high altitude flight, etc. On top of it, it was quoted that the look of Mark 2 was to be a pure metal, a look as if it were a kit of some kind done by Stark before he got to and refinished the suit to make the red/gold we all know. The reason it shines so much is because of the lighting in Stark's workshop, when he goes out flying around Los Angeles, the finish is flat.
This opening scene is why people think chrome:
Now if you continue watching that scene you'll see that right outside of the shop in the night sky the finish is obvious, its brushed metal which is just standard metallics just really polished because it picks up the reflections of whatever is shone on it.
You can even in some shots see the "grain" from the polishing.
Another interesting note is that when you really watch the film you see that the "circular stamps" as someone noted is accurate, take a look at this still:
The rivets are flat as if punched into the metal to hold the parts together. Looks like this:
Is more accurate then we've given it credit for. You can also see it in the first frame I posted. Looks like anything done with raised rivets is actually idealized and inaccurate.
:emperor pass then for me 
