The phrase "special coating" refers to a special layer or material that is added to protect or enhance an object's appearance or functionality. Full definition
A truly special coat that should be out for every occasion... how does that saying go? (acolourfulcanvas.com)
«Right now we're looking at special coatings for windshields that prevent raindrops from forming on the glass to block visibility,» he said. (articles.orlandosentinel.com)
Special coatings on the glass can impede the interior heat from radiating to the outside, making the house an even more efficient heat trap. (psmag.com)