calculation of the surface "exposed"

[LagunaSeca]

Good morning to all,
as described in the title, I should find the way to calculate the exposed surface of a component in order to attribute a value for painting. example: in a welded structure there are several areas in contact with others that are to be subtracted to the overall calculation.

using this value, I could go to attribute the amount of paint I need for the exposed areas.

Does anyone have any ideas?
Thank you.

 

[stefanobruno]

make a derivative component with " union joints ..... " and then visualize the resulting area in iproperty.

 

[LagunaSeca]

Thank you very much for the answer.
Yes, it is a solution but not exactly what I need. In practice I would need this value to end up in custom iproperties so that it is passed to management during the export of the distinct. this for each piece that is saved/archived.
the proposed solution is great on the single piece but if I have so many pieces to process, it becomes a bit expensive and above all having to do it manually, there is risk of errors.