[sandy25]

Can somebody tell me how to identify the occurence of damage to car's door or other metal part with the help of any spray or other device.

        For example if my car has been in accident two years back (and my left front door is damaged) and once again in new accident which is happened 2 months back (and this time my right front door is damaged).

         So is there any method to find out difference between occurence of two accidents?

[Corribus]

What do you mean by "damage"?

Presuming paint has been removed during the damage, the older damage will likely have more rust buildup. However it will be hard to normalize for other confounding factors, such as the size of the damaged area, and so forth.

Maybe by providing a little more information it would be easier to give some help. Also, since the damage is mostly physical in nature, a chemical solution may not be the most appropriate.