These Hexagon Nuts and Washers are bright zinc plated for increased corrosion resistance. The hexagonal shape of the nut is designed to be driven by a wrench (spanner) and provides excellent torque when done so. The washer distributes the load of a the nut and helps to reduce vibration.
Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier and by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrate’s surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminum and stainless steels by their oxide layers.