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How to check for Good Galvanization

August 22, 2011

Hi,

How could we make sure that the hardware we bought (like screw, keys, hexagonal L keys, nuts) has good galvanization and could last for couple of years? Do you have any inputs or inspection criteria to be considered in analyzing good hardware? Thank you.

Regards,

Luichito Durban
buyer - Vietnam

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Sir:

Zinc corrodes about 20 times slower than iron, and it protects the steel until almost all of the zinc is gone. The lifetime of the product is directly related to the thickness of the zinc, thus hot dip galvanized which is thicker than electroplate zinc will last much longer. Around the ranch here I always try to use hot dip galvanized product because for me it lasts a lifetime.

Most hot dip galvanized steel has between about 50 microns to about 200 microns of zinc on it. For electroplated zinc the zinc coating thickness will likely be a fraction of a micron to at most a few microns.

For outdoor products I recommend hot dip galvanizing.

Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA
August 26, 2011

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Dr. Cook is right that electroplated zinc is much thinner than galvanized zinc, and I would agree that galvanizing is a more appropriate finish for outdoor exposure. But about 5 microns (2 ten thousandths of an inch) would probably be the most common spec, with thicknesses from about 4 microns through 15 microns being readily available.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 29, 2011