Just beginning my 10 empennage kit. In Van's construction manual it mentions all aluminum bar, angle, and tube used in the RVs, especially the main spar bars, must be primed or anodized to assure corrosion resistance. Aside from prime or not, what are some examples of parts that are aluminum bar, angle, and tube. I could guess but would like to hear some part names so I have an idea what is meant. Also I have wondered in Alclad parts, when holes are drilled or drilled to size, the inside part of the hole is not Alclad metal. Why is that not primed?