Material affect to antenna Gain

I have an Yagi antenna which made from alumina.
To embrace the sufference from environment, it is suggested anodize aluminum and paint on it.

But I wonder some critical might be affected: Gain, Efficiency,..? because when anodzing there's an dielectric material stay on surface and affect to radiation efficiency of antenna.

Pls advise.

Think! Aluminium oxyde is a good dielelectricum, a thin layer don't affect antenna performance, also most paints won't. Any semiconducting material however can.

I think you cannot have a "Yagi made of Alumina". Alumina is ceramic material and not conductive. Aluminum is probably the material of your antenna. As the wavelength is much longer than the thickness of the anodized or paint layer, you do not need to worry about its effect on gain. Even iron Yagis with a thick paint function well.
Learn about the "penetration depth" or skin-effect, then you can understand the problem.

Should be OK ,don`t worry.