Pros and Cons of hot deep galvanized bolts

Bolt and nut

Hot deep galvanized bolts used to be dominant in bolting industry a while ago, however they are replaced with Dacromet coating in the modern engineering world due to the hardships and problems they had. here we describe some of the advantages and disadvantages of hot deep galvanized bolts.

Advantages of hot deep galvanized bolts

Hot deep galvanizing process happens at a very high temperature of about 425-450 degrees centigrade. at this temperature zinc penetrates the surface of the metal and provides a thick layer on top of the surface. this layer is highly protective and even deep scratches on the surface dont make the bolts vulnerable against stain and humidity.

Disadvantages of hot deep galvanized bolts

A. Due to the very high temperature of hot deep galvanizing process, many high tensile bolts and nuts that have been tempered and quenched are exposed to a phenomenon called Hydrogen embrittlement, which causes the bolts to have reduction of tensile and subsequently break at lower stress.

The layer that hot deep galvanization leaves on top of the bolt is significant, roughly 35-80 microns depending on the bolt diameter. this causes fastening problems at the time of bolt and nut assembly, for which to be solved, the nuts should be oversized, the process that makes the nuts vulnerable once more against corrosion.