No passwords, No popups, No cost, No AI:
we earn from 'affiliate link' purchases, making the site possible

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

-----

PHOSPHATING

IN DIP PHOSPHATING, SEVEN TANK PROCESS, I AM FACING YELLOW STAIN PROBLEM. AFTER HOT SUL.ACID PICKLING, THE COMPONENTS GOES TO DIP HOT CLEANING. AFTER PICKLING COMP. SOME AREA LOOKS LIKE ETHCHED ( POLISHED). THESE AREAS GOT YELLOW COLOUR IN DIP HOT CLEANING. AND ALSO LOOKS YELLOW AFTER PHOSPHATING. HOW TO AVOID THIS PROBLEM. WHAT IS THE INCREDENT MAKE IT YELLOW IN CLEANER.

GOVINDAN.R
TI CYCLES OF India - Chennai, India

You say you are acid cleaning, then alkaline cleaning. If you are not rinsing properly between the two stages and the acid is reacting (forming salts) in the alkaline, this could be leaving sulfur stains. Why are you not alkaline cleaning/rinse/acid pickle/rinse/phosphate/rinse/seal/oil, this is the usual sequence. The etched/polished you see may actually be an oily surface which has not been acid cleaned.

Wayne McKee
McKee Specialty - Mississauga, Ontario, Canada

It sounds like a rinsing problem to me. Check water rinses and dwell times between each stage. Also check the hot H2SO4 is not drying out between processing and rinsing. Check Fe content or accelerator content of phosphate (if Zn) if Fe check free acidity.

Good Luck,

Alex Jennings
- UK

(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: