This a micrograph of copper oxide deposits on nickel plating. The copper oxide is inhibiting the electrical conduction of a 120V light on terminals of a light bulb. This is an environmental failure stemming from the fact that the exposed copper on another part of this circuit, deposited copper oxide by arching, and this, in turn, caused an eventual loss in conduction to the bulb.
This arcing happens when low-level contaminants are present and concentrate over time. Once a copper oxide barrier forms, the resistance increases and arcing soon occurs on the deposited surface. This could end in either a fire or no conduction depending on environmental conditions existing at the time of the failure. This failure occurred in a museum which one would think had minimal contaminants. The analysis was performed on an SEM-EDS Gideon Analytical Labs has the capability and expertise to help clients from a variety of unrelated fields to understand the nature of environmental failures caused by excessive cleaning fluids, pressure washers, light exposure, accumulated chemical effects, and electrical conditions. We have been analyzing failures for over 30 years. We have EE, chemists, component, and analytical people to do the job right. Call us.