The armor structure is done quite well, but armor gains a lot of its definition from shading and texture (as well as color, depending on your choice of medium).
You've definitely got shading and use of light down quite well, the only thing I would've done differently is possibly add some age to the more exposed areas (cracks. scrapes, gouges) and made use of negative shading on the indents in the armor. (Specific example being the dark line on the elbow guard).
However, despite creative differences in style and experience, I applaud your artwork. Very well done.