Passivation Services per ASTM A967 & QQ-P-35 & AMS 2700
Artistic Plating Company is an industry leader in both nitric and citric acid passivation services to ASTM A967, QQ-P-35 and AMS 2700 specifications. Artistic provides competitive high-volume commercial passivation services as well as precision passivation services utilizing ultrasonic generators for demanding applications within the medical and dental industries. Artistic Plating’s passivation services are currently employed in numerous sectors including the medical, dental, aerospace, automotive, appliance, power distribution and food processing industries.
Artistic offers a full range of stainless steel passivation services including all methods listed within ASTM A967, QQ-P-35 and AMS 2700. If needed, Artistic Plating can meet the requirements of any “custom” company specific nitric or citric acid passivation method. In addition, Artistic can also employ specialized passivation services such as the AAA process to passivate even the most difficult alloys including high-sulfur free machining 303 or 416 alloys as well as high chromium alloys such as 440 stainless (Reference AAA Passivation Methods article in our Metal Finishing White Papers section). Inhibited passivation solutions are available to maintain bright surfaces of stainless components such as machined faces and centerless ground shafts.
Unfortunately very few part blueprints indicate the specific passivation method to be used. This opens the door for “brand-x” job shops to use any convenient method resulting in a part that has been passivated but is not truly passive (reference: My passivated “stainless” steel product is exhibiting corrosion, how can this be prevented? in our Plating Topics section).
Artistic’s Plating’s extensive experience in stainless passivation services ensures that the correct passivation method will be selected to match the specific stainless steel grade. Artistic plating provides full in-house testing services to certify the performance of our passivation services including high humidity, salt spray per ASTM B117, potassium ferricyanide and copper sulfate.
What is Passivation of Stainless Steel?
Stainless steel or corrosion-resistant steel (CRES) is defined as a steel alloy with a minimum of 11% chromium content by weight. Many alloys of stainless steel include substantial nickel to further enhance the corrosion resistance. In general, stainless steel is broken down into three main groups based upon the alloying elements and compositions as follows: 1) Austenitic Grades (all 200 & 300-series), 2) Ferritic Grades (part of the 400-series, low carbon alloys) and 3) Martensitic Grades (part of the 400-series, higher carbon alloys).
The reason for the stain-less nature of stainless steel is due to the formation of a thin, adherent and passive (read non-reactive) film of chromium oxide that prevents further surface corrosion of the stainless product. This is in stark contrast to iron oxide (red rust) that forms on plain carbon steel products which is a loose oxide that actually accelerates corrosion by forming additional iron oxide.
It is important to note that stainless steel is just that – stain-less and not stain-proof. The degree of corrosion resistance of a stainless alloy is a function of the alloying composition, heat treatment, and internal stresses due to forming/machining. An example of this is phenomena is 303 free-machining stainless steel which has notably less corrosion resistance than 304 stainless steel due to the higher concentration of sulfur and phosphorous that imparts the desired machinability of the 303 grade.
When stainless steel products are manufactured free-iron is generally transferred to the surface of the material from the cutting, stamping and forming tools used in the manufacturing process as well as mechanical graining (belting) operations. Free-iron can readily oxidize forming visible rust on the surface of the product objectionable to the end consumer. Passivation is a chemical treatment with a specific acid formulation that removes any free-iron or other contamination from the surface of the stainless steel while promoting the uniform formation of the passive chromium oxide layer.
Stainless Steel Passivation Specifications
The two most common passivation services certified by Artistic Plating are ASTM A967 and QQ-P-35. Artistic Plating also can certify our passivation services to ASTM A380, ASTM F86, AMS 2700C, ISO 16048 as well as most company-specific passivation specifications. A summary of passivation services per the common ASTM and MIL specs is as follows:
Passivation to ASTM A967
Five nitric and citric methods are listed as follows:
Nitric 1: 20-25 v% Nitric Acid, 2.5 w% Sodium Dichromate, 120-130F, 20 Mins minimum
Nitric 2: 20-45 v% Nitric Acid, 70-90F, 30 Mins minimum
Nitric 3: 20-25 v% Nitric Acid, 120-140F, 20 Mins minimum
Nitric 4: 45-55 v% Nitric Acid, 120-130F, 30 Mins minimum
Nitric 5: Other combinations of temperature, time, and acid with or without accelerants, inhibitors or proprietary solutions capable of producing parts that pass the specified test requirements
Citric 1: 4-10 w% Citric Acid, 140-160F, 4 Mins minimum
Citric 2: 4-10 w% Citric Acid, 120-140F, 10 Mins minimum
Citric 3: 4-10 w% Citric Acid, 70-120F, 20 Mins minimum
Citric 4: Other combinations of temperature time and concentration of citric acid with or without chemicals to enhance cleaning, accelerants or inhibitors capable of producing parts that pass the specified test requirements.
Citric 5: Other combinations of temperature time and concentration of citric acid with or without chemicals to enhance cleaning, accelerants or inhibitors capable of producing parts that pass the specified test requirements. Immersion bath to be controlled at pH of 1.8-2.2
Five testing methods to validate passivation services are provided as follows:
Practice A – Water Immersion Test
Practice B – High Humidity Test
Practice C – Salt Spray Test
Practice D – Copper Sulfate Test
Practice E – Potassium Ferricyanide-Nitric Acid Test
A table of recommended nitric acid passivation services is provided in the appendix that correlate Nitric 1 through 5 methods to the specific stainless steel alloy grade. No such reference is provided in the specification for Citric 1 through 5 methods.
Passivation to QQ-P-35
QQ-P-35 does not cover citric acid passivation services. Four active nitric acid passivation services are covered as follows (four inactive methods have been withdrawn):
Type I – Withdrawn
Type II – 20-25 v% Nitric, 2-2.5 w% Sodium Dichromate, 120-130F, 20 Mins minimum
Type III – Withdrawn
Type IV – Withdrawn
Type V – Withdrawn
Type VI – 25-45 v% Nitric, 70-90F, 30 Mins minimum
Type VII – 20-25 v% Nitric, 120-150F, 20 Mins minimum
Type VIII – 45-55 v% Nitric, 120-130F, 30 Mins minimum
Four testing methods to validate passivation services are provided as follows:
4.4.1.1 – Water Immersion Test
4.4.1.2 – High Humidity Test
4.4.2.1 – Salt Spray Test
4.4.2.2 Copper Sulfate Test
A table of recommended nitric acid passivation services is provided in the appendix that correlate Type II, VI, VII & VIII methods to the specific stainless steel alloy grade.
Stainless Passivation Services – Why Artistic Plating?
Artistic Plating provides expertise in passivation services to fulfill even the most demanding applications. From prototyping and PPAP qualification to full production processing – it is Artistic’s dedicated effort to exceed your expectations. The following points highlight why Artistic Plating is a leader in passivation services:
- Precision Passivation: Artistic has worked with numerous manufacturers to solve existing passivation problems where stringent cleanliness, appearance and corrosion performance was required. We have the ability to use ultrasonic generators in our passivation services as well as in the final rinsing steps if required. These systems allow proper passivation of complex geometries or even very small and intricate parts such as those used in the medical and dental industries.
Competitive Commercial Line: In addition to our precision passivation services Artistic offers extremely competitive commercial grade passivation on a high volume production line. This guarantees the most competitive pricing in the industry on high volume commercial grade components. - Grade-Specific Passivation: Many finishing companies passivate all stainless steels the same - just dip and ship! At APC we are experts in matching the passivation method to the specific material grade. This results in parts that are passivated correctly with results that can be validated and certified.
- Any Specification Anytime: If you need to certify passivation services to a company specification that is "outside the normal" we can help. We can and will setup specific acid and inhibitor chemistries to service you with multiple step processes such as the AAA method of passivation.
- RoHS and REACH Compliance: Artistic is at the forefront of environmental compliance and can certify many of our passivation services as needed to the current RoHS, ELV and REACH regulations.
- Competitive Pricing: Artistic Plating has been providing quality passivation services for over sixty years. Competitive pricing in passivation services is paramount to gaining and maintaining our customers in today’s competitive global marketplace.
- Lean Lead Times: With inventories leaner than ever, rapid turn around is an underpinning core company value to ensure the service our customers need in passivation services.
- Value Added: Artistic prides itself on meeting the customer’s needs. Whether it’s custom engineering packaging, Kanban inventory management, light subassembly or multiple finishing combinations – Artistic will work with you to ensure we meeting your needs in passivation services.
- Extensive in House Analytical and Quality Lab Services: SPC is employed in all wet-lab work surrounding our passivation services to ensure baths are analyzed and adjusted at optimum frequencies to maintain operation between critical upper and lower control points. Our quality lab employs the latest technologies to inspect your parts and will work to your requirements to provide testing as needed. Our quality lab can certify our passivation services to any of the test methods outlined in the ASTM or MIL specs.
