Passivation | ASMT-A967
Nitric Acid
- Removes free iron from the SS substrate…
- Achieves a passive surface…
- Meets QQP-35C (replaced by ASTM A967 [AMS-QQ-P-35])…
- Tested and approved by the aerospace, medical, machining/manufacturing & food industries…
- Brightens 300 series SS alloys…
- Not as bright of an appearance on 400 series SS…
- Low operating pH…
- <3.0 for all series of SS
- Higher metal removal rate 0.0028 mills/minute per surface (performed on 303 SS)…
Citric Acid
- Removes free iron from the SS substrate…
- Achieves a passive surface…
- Meets QQP-35C (replaced by ASTM A967 [AMS-QQ-P-35])…
- Tested and approved by the aerospace, medical, machining/manufacturing, & food industries…
- Brightens 300 series SS alloys…
- Excellent appearance on 400 series SS…
- Operates at a higher pH…
- 3.0-3.2 for 400 series SS
- 4.5-5.0 for 300 series SS
- Lower metal removal rate
- 0.0010 mills/minut per surface (performed on 303 SS)…
- Accepted as an alternative to nitric acid/sodium dichromate for AMS-QQ-P-35 Type
II on 303 SS (less chance for pitting)…
DS-9 System
- Reflective finish on high nickel allows (SS, Inconel, Kovar)…
- Achieves passive Nickel rich surface…
- Promotes an extremely smooth surface…
- Excellent deburring characteristics…
- Autocatalytic chemistry – essentially no shadowing…
- Excellent for…
- Intricately designed parts…
- Small to medium size parts…
- Thin walled parts – no potential of burn through…
- Controlled metal removal…
- DS-9 is listen on many medical, defense, & aerospace specifications…
The new specification for passivation – ASTM A967 – replaces QQ-P-35C (Cancellation
notice dated: November 14, 1997). ASTM A967 allows the use of the new citric acid
solution as well as the nitric acid solutions covered in QQP- 35C.
In the last 10 years citric acid solutions have evolved, improving on performance,
and reducing costs. In light of the risings costs associated with the nitric system,
citric acid becomes a competitively priced alternative.
Please contact Twin City Plating for current test results of citric acid passivation
systems. Also available are papers and technical data on both Passivation and Electropolishing
of stainless steel alloys.
TCP Passivation Brochure.pdf