Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

finishing.com -- The Home Page of the Finishing Industry

  The authoritative public forum
  for Metal Finishing since 1989

-----

Black spots from storing galvanized parts in pickling area

Q. The storage area of our galvanized fastener is nearby to the pickling area, around 100 meters. We have found that a few days after galvanizing, small small black patches were found on a few concentrated areas of the bolts. Is environmental condition the issue behind this?

Kirt Shar
galvanized fasteners - vizag, andhra pradesh, India
September 24, 2015

User's Guide to Hot Dip Galvanizing for Corrosion Protection in Atmospheric Service
by NACE
[only rarely available]

on AbeBooks

or eBay or

Amazon

(affil links)

A. Hi Kirt. It's probably not possible to say that the storage conditions are the only problem or the chief problem when we know little else ... but it is certainly right to say that pickling fumes, even in low concentration, will very rapidly attack galvanizing, so that storing galvanized parts in the vicinity of galvanizing fumes is a recipe for ruining them.

Remember that zinc is very rapidly and severely attacked by acid. Good luck.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2015

Q. Dear sir,
Thanks for your reply. We have maintained all the parameters as well. Also the surface finish is good too after being galvanised. Still the problem is being faced by us.
One more problem being faced is that the nuts after getting tapped are developing a very dull look. A few dark patches are observed too. We are using proper lubrication. What might be the reason for this?

Kirt shar
galvanised fasteners - Vizag, A.P, India
September 24, 2015

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: