Galvanizing Bolts FAQs

Galvanized Bolts and Chased Threads

Can threads be chased after hot-dip galvanizing for proper nut fit?

Absolutely not! Externally threaded fasteners should never be “chased”. During the hot-dip galvanizing process, excess zinc has a tendency to build up in the threaded portion of a fastener. Chasing threads is a term used to describe re-cutting threads after galvanizing to remove this excess zinc that has accumulated during the galvanizing process. Chasing threads... Read more

Weight Gained from Galvanizing

How much weight is gained from hot-dip galvanizing bolts?

According to the American Galvanizers Association (AGA) the weight of an item on average will increase about 3.5% from the zinc added during the galvanizing process. However, the AGA goes on to say, “…that figure can vary greatly based on numerous factors. The fabrication’s shape, size, and steel chemistry all play a major role, and... Read more

High Strength Bolts Coatings

What corrosion-resistant coatings are available for high-strength (over 150 ksi) bolts?

Due to hydrogen embrittlement concerns ASTM recommends against hot-dip galvanizing , mechanical deposition, or electroplating with zinc or other metallic coatings on high strength bolts ultimate tensile strengths that exceed 150 ksi. So what are the alternatives to provide corrosion resistance for A490 structural bolts? Protective Coatings ASTM states that if a protective coating is... Read more

Galvanized Nuts Tapped Oversize

Can I use black (plain finish) or zinc plated nuts on galvanized bolts?

No. Hot-dip galvanized nuts need to be used with hot-dip galvanized bolts since galvanized nuts are tapped oversize to accommodate for the extra 2 – 6 mils (.002 – .006) of zinc that is added to the threads of the bolt during the galvanizing process. A common misconception is that bolts that are going to... Read more