ASTM A153 governs zinc coatings applied by the hot-dip process on iron and steel hardware, including nails, bolts, nuts, fasteners, and rods.  The hot-dip galvanizing process for articles galvanized to ASTM A153 is identical to the process required under ASTM A123 with the exception the iron and steel hardware in ASTM A153 are centrifuged or spun to remove excess zinc.  This is reflected in the coating thickness required by ASTM A153 being slightly less than those required under ASTM A123.  Table 1 of the specification calls out the thickness or weight (mass) of zinc coating required for various classes of material.  Classes of material are based on thickness and length. 

This specification also prescribes finish & appearance, sampling, test methods and inspection of the finished part.

More Info:
Hot-Dip Galvanized Fasteners

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Mark Bartnik

What is the expected k factor (sometimes called nut factor) for 25 microns inorganic zinc silicate coated A193 Grade B7 nuts and bolts?  Assume M30 bolts at 3.5mm thread pitch and M36 bolts at 4.0mm thread pitch.

Laura Hanson

Hi Mark,

The difference is in the coating characteristics of the finishes. More information regarding electroplating and zinc plating coating characteristics can be found on our site: and and in our Zinc Coatings publication:

Mark Tellis

What is the difference between Hot dip galvanzing and Zinc electroplating.?

Customer is stating supplied spring wahers are electroplated!  is there any clue to defend that it is Hot dip galganzed.

Please reply.  it is very important.

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