Varnish, ASTM D3955 is the only authorized type of which coating?

Varnish, as specified by ASTM D3955, is recognized specifically for its use in fungus-proof coatings. This standard emphasizes properties related to inhibiting the growth of fungus, which is crucial in environments where moisture can lead to biological degradation of materials. The importance of this coating becomes evident in aircraft applications, where maintaining the integrity and functionality of avionics systems is critical. The varnish’s chemical composition and application methods are designed to create a protective barrier that effectively prevents fungal growth, thus ensuring the longevity and reliability of the coated surfaces.

In contrast, other types of coatings mentioned are governed by different standards that address their specific functions, such as corrosion resistance, thermal insulation, or conductivity. Each of those categories relies on different materials and properties distinct from those outlined in ASTM D3955 for varnish meant to control fungal growth. Such distinctions highlight why varnish is uniquely suited and authorized for use as a fungus-proof coating.