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Anodizing Industry-Phosphoric Acid

Q. We supply Phosphoric Acid 85% (Technical Grade) to various industries. Anodizing Industry being one. The specifications are:

"adhesive Bonding of Aluminum Alloys"
by Edward Thrall

on AbeBooks

or Amazon

(affil links)

Assay: 85%
  Density: 1.684 at 20 Deg.C
  Arsenic: 60 ppm max
  Iron (as Fe): 20 ppm max
  Chlorides (as CI): 10 ppm max

A few of our customers desire 86.4% material, as they claim that it gives excellent coating and shine with this extra 1.4%. They use products of this specification:

Phosphoric Acid (as H3PO4)% min 86.4 P2O5 Content % min 61.5 Specific Gravity min at 20°C 1.689 Arsenic (as As) ppm max 0.1 Kindly clarify, if this difference of 1.4% can actually make a big difference in anodizing on aluminium. What is the specification of Phosphoric Acid best suited for Anodizing industry.

Jatin Aggarwal
- New Delhi, India

A. For anodizing use Phosphoric Acid 75 or 85% meeting Federal Specification A-A-55820 with a maximum of 25 ppm chlorides.

Ray Handwerker
Brenner Tool & Die, Inc. - Bensalem, Pennsylvania, USA

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