Why is a violet-light flashlight used in coating inspections?

A violet-light flashlight is specifically used in coating inspections to check for holidays, which are uncoated areas in a coating system that could lead to corrosion or other issues. The violet light is effective because it can highlight inconsistencies in the coated surface, making uncoated spots more visible. This is crucial in maintaining the integrity of the protective coating, as even small holidays can compromise the performance of the coating by allowing corrosive elements to reach the substrate.

In contrast, enhancing color fidelity would relate more to visual inspections where color matching is important, rather than identifying uncoated areas. Measuring thickness typically requires different tools such as micrometers or magnetic thickness gauges, and determining adhesion strength involves tests like tape pull or crosshatch adhesion tests, neither of which are the function of a violet-light flashlight. Thus, the main purpose of using this flashlight in coating inspections is effectively to identify holidays.