# Coatings

A coating can be applied to any wires or to both sides of a conducting face.

The following must be true when adding a coating to a face:
• One side must have free space.
• The other side must have free space or PEC.
The following coating thickness requirements apply when using the MoM / MLFMM, PO or RL-GO solution methods:
Solution Method Coating Thickness Requirement CO Card Equivalent
MoM / MLFMM Both electrically thin and geometrically thin Electrically thin surface coating
MoM / MLFMM Electrically thick, but geometrically thin (single layer).
Note:
• Only for closed structures with a PEC surface and the normal vector pointing towards the source(s).
• Coating is applied to both sides of the PEC surface, since fields will be zero where there is no sources.
Dielectric / magnetic surface coating (single layer)
PO Electrically thick, but geometrically thin Dielectric / magnetic surface coating
RL-GO Both electrically thick and geometrically thick Dielectric / magnetic surface coating
Note: A geometrically thin coating must be thin relative to the triangle size (and as a result also to the free space wavelength) as well as the curvature radius of the surface.