Which tool is commonly used to measure surface profile before applying a coating?

The most commonly used tool for measuring surface profile before applying a coating is a profilometer. This instrument is specifically designed to assess the roughness or texture of a surface, which is crucial for ensuring proper adhesion of coatings. The measurement obtained from a profilometer provides vital information about the peak heights and trough depths on a surface, helping to determine if it meets the necessary standards for coating application.

In contrast to other tools listed, a caliper is typically used for measuring dimensions such as thickness or diameter rather than surface texture. A thermometer measures temperature, which is unrelated to surface profile assessment. Painter's tape is utilized for masking during painting, not for measuring surface characteristics. Thus, the profilometer stands out as the specialized tool tailored for evaluating surface profiles before coating applications, ensuring optimal results and durability of the finish.