Letter 37059

Peeling after 180 Degree bend test [China] 

+++++

I did EN over Al. One of the criteria spelled out is no peeling after a 180 degree bend. Though it's not really peeled off, some blisters can be seen especially near the edge.
Any advise will be greatly appreciated.

Robert You
Job shop plater - China

A 180 bend test is a very rigerous test for EN on aluminum.
You need a superior zincate and an excellent strike. Are you using the largest allowed mandrel for the test?

James Watts
- FL

While the coating will crack perpenducular to the bend, it should not flake, peel, blister, or otherwise come loose from the substrate.

Poor adhesion is almost always because of inadequate pretreatment. You do not say how you cleaned the coupons.

Ron Duncan Palm International, Inc. - LaVergne, TN

Ed. note: It is our sad duty to alert the readers to the passing of Ron Duncan on Dec. 15, 2006. For those who would like to know more about him, a brief obituary opened Update No. 13 of our Metal Finishing Industry Update Podcast.

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