The components that form a bolt can be identified in three sections. The head is the part of the bolt with the largest diameter, which provides a mount for tools to either apply or resist torque. It also provides part of the bearing surface for substrates being bolted. The shank of the bolt is the longest part of the bolt and has external, helical threads on its circumference. This piece is responsible for the alignment of the workpieces. Finally, the end opposite of the head is known as the chamfer, which provides a slightly beveled edge to aid the bolt's insertion into holes and nuts.
The hot dip galvanized coating does not perform well in a salt-spray test chamber. In order for the zinc in the hot-dip galvanizing to perform as it was designed, it needs to develop a patina layer composed of zinc carbonate. This layer is very stable and non-reactive which gives the galvanizing its desired properties, but in order to form this patina, the zinc must go through wetting and drying cycles such as those that would be encountered in a real world environment. In an ASTM B117 salt spray chamber, the environment is kept continuously wet which basically washes off the necessary corrosion resistant products that would otherwise be produced naturally by the galvanizing. Therefore, the hot dip galvanizing appears to have a poor salt spray corrosion resistance, but this type of QC testing isn't really applicable for hot dip galvanized coatings.