The UV light emitted by the UV LED lamps itself cannot penetrate the metal plating because of the metal's property of reflecting and absorbing UV light.

Most metal plating, such as chrome, nickel or copper, reflects most of the UV light without allowing the light to penetrate to the substrate below. However, if there are small defects, cracks or holes in the plating, it is possible for UV light to pass through these defects and affect the coating or substrate below.

In addition, for some transparent or semi-transparent plating layers of special materials (although this is rare), there may be some degree of UV light penetration. 

If you are considering the use of UV LEDs on plated products, such as UV coatings used to cure the surface after plating, then the key is whether the UV light can reach the surface of the coating. 

If the plating layer is completely closed and not transparent, then the UV light will not be able to reach and cure the coating. In this case, it is often necessary to finish curing the UV coating prior to plating, or to use a coating that does not require UV light curing.