Melling pump cover bolt torque

Does your paper work say exactly which coating they used? The have some that are only .0002-.0003 thick and that's what I'd ASSume they used but I could be wrong.

They have coatings that can close up piston clearance by up to .020 so that's something I may use on a vintage dirt bike I need to make run.
WHY WOULD U FEEL THE NEED FOR COATING THE INSIDES? The pumps are only supposed to have .00125 to .004 to start with !!