Metal finishing Q&As since 1989
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Improving pretreatment for slider painting
"Zipper: An Exploration in Novelty"
by Robert D. Friedel
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Q. WE ARE MANUFACTURERS OF HIGH QUALITY SLIDERS MADE OF ZINC ALLOY IN AUTO DIE CASTING MACHINES.WE NORMALLY USE PHOSPHORIC ACID, SODA ASH AND POTASSIUM NITRATE MIXTURE OR ALTERNATIVELY HYDROCHLORIC ACID TREATMENT AND LATER CHROMIC ACID DIPPING TREATMENT FOR phosphatING THE SLIDERS BEFORE WE PAINT THEM WITH EPOXY PAINT IN ROTATING BARRELS(15 KG CAPACITY) THE COATING OF THE PAINT IS NOT LONG LASTING ? CAN YOU SUGGEST ME ANOTHER ALTERNATIVE PRE TREATMENT/phosphatING SYSTEM FOR A LONGER LASTING PAINT RESULT.
RAJEEV CHAWLA- KOLKATA, WEST BENGAL, INDIA
2004
A. Dear Mr Rajeev,
Why don't you just degrease them in a suitable proprietary non-ferrous cleaner and directly zinc phosphate using a proprietary process? You may need to include a 1% Hydrofluoric acid dip in between as well if your zippers are patchy and have not phosphated well.
Khozem Vahaanwala
Saify Ind
Bengaluru, Karnataka, India
2004
"Phosphating of Metals"
by Werner Rausch
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Q. I want to know about pre treatment phosphating for powder coating. I want full details of phosphating and the chemicals used for it. And also the procedure of eight tanks.
Vasanth Raj. N- Chennai, Tamilnadu, India
2004
A. Hi Vasanth. I can offer this brief outline that the procedure includes soak cleaning, acid activation, zinc phosphatizing, and passivation -- with rinses in between, and that most people call it "the 7-step process", although 8 steps is possible.
We can also offer answers to any highly specific question you pose. "Full details of phosphating and the chemicals used" fills books, of course, and we can refer you to them as well.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 2022
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