Metal finishing Q&As since 1989

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PICKLING PROCESS

I WOULD LIKE TO KNOW WHY RUST TYPE OF MARKS APPEAR AFTER SHEET PICKLING? AND ALSO IN PUSH PULL PROCESS OF PICKLING HOW LONG SHOULD THE COIL TAKE TO PASS THROUGH THE RINSING AND NEUTRALIZING TANK AFTER PASSING THE ACID TANK?

PHILIP JACOB
- Chennai, Tamil Nadu, INDIA
2001

The brown mark is Stain mark due to oxidation. When strip is pickled it need to be rinsed immediately. If the pickled surface is exposed to oxygen due to line stop for more than 3 to 5 minutes it could cause this type of Stains.

There are special methods to remove this stain either by having a loop at entry so that whenever the line is stopped due to the stitching time the loop could inch the material so that rinse process is continuous or alternatively the rinse could have flooding arrangement. There are special stain free rinse units available to overcome this problem.

The rinse time is normally controlled by the line speed and it is also controlled by the rinse water spray quantity so as to maintain a Cl level less than 2 mg/sqM after rinse. Normally for a speed of 100 MPM the rinse dwell time could be 6 seconds.

Jagannathan Rajagopalan
DBI, USA - Irving
2003

TELL DETAIL ABOUT ;PICKLING PROCESS HOW IT IS DONE WHICH CHEMICAL USE IN THIS PROCESS AND WHY? WHICH MACHINES INVOLVED IN THIS PROCESS

ARVIND SURESHRAO SUROSHE
UTTAM GALVA STEEL,LIMITED - KHOPOLI, MAHARASHTRA, INDIA
2006