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Inspection & Test for Zinc+Yellow Bolts

Sirs, I need to introduce a goods inwards inspection & test procedure to measure the integrity of zinc yellow passivated bolts,can anyone suggest a quick and simple test which validates the plating process? many thanks

Chris Bumstead
T M Products - UK
2000

There are a few ways you could go about validating the quality of a zinc yellow finish on your bolts.

You could use regular salt spray testing to evaluate the corrosion resistance of the bolts. This can be used to check a batch and is reliability. Of course, this takes lots of time and can not be used on a bolt that you want to sell afterwards.

You can check plating thickness. There are machines available where a technician can touch a measuring device to the bolt, and you can get a measurement of how many microns of plating are on the bolt.A normal plating thickness for zinc yellow would be about 8 to 12 microns or so, but you will need to develop your own guidelines. This type of measurement does not damage the bolt.

You can also visually inspect the bolts. The zinc yellow plating should come out with a certain color. If the color changes, or if spots start to show up on parts, then you will want to immediately troubleshoot your process. This method is not highly scientific, but is very inexpensive.

You may want to do a combination of the above or look for additional methods. I hope this helped!

Tim Neveau
Rochester Hills, Michigan
2000