Indeed it's not always easy to tell chrome plating from other finishes if the parts are not side by side. Chrome plating is more reflective than a painted surface and more specular, the reflection is deeper, less distorted, more mirror-like than other finishes. A sign of a great chrome surface is that you can clearly see the clouds in the sky reflected in chrome plating. And there's a hard to define "glint" to top quality chrome plating that nothing else has to display.

Hard chrome plating is almost always applied to items that are made of steel, usually hardened steel. It is metallic in appearance but is not particularly reflective or decorative. Hard chrome plating is not a finish that you would want on a wheel or bumper. There are variations even within hard chrome plating, with some of the coatings optimized to be especially porous for oil retention, etc., others "thin dense chrome", and so on. Many shops who do hard chrome plating do no other kind of plating at all, because their business is designed to serve only engineered, wear-type, needs.

 

Decorative Chrome Plating

Decorative chrome plating is sometimes called nickel-chrome plating because it always involves electroplating nickel onto the object before plating the chrome (it sometimes also involves electroplating copper onto the object before the nickel, too). The nickel plating provides the smoothness, much of the corrosion resistance, and most of the reflectivity. The chrome plating is exceptionally thin, measured in millionths of an inch rather than in thousandths.

When you look at a decorative chrome plated surface, such as a chrome plated wheel or truck bumper, most of what you are seeing is actually the effects of the nickel plating. The chrome adds a bluish cast that protects the nickel against tarnish, minimizes scratching, and symbiotically contributes to corrosion resistance. But the point is, without the brilliant leveled nickel undercoating, you would not have a reflective, decorative surface.