ASTM A967 PDF

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Passivation of stainless steel is a process that removes free iron from the surface of a stainless component and at the same time promotes the formation of a thin, dense oxide protective barrier. APT provides both competitive high-volume commercial stainless steel passivation as well as precision medical passivation of titanium and other medical-grade alloys including cobalt chromium, MP35N and LVM, utilizing ultrasonic systems for demanding applications within the medical and dental industries.

This is in stark contrast to iron oxide red rust that forms on plain carbon steel products. Iron oxide is a loose, scaly oxide that easily falls away to allow the formation of additional iron oxide, thereby perpetuating the corrosion reaction. When stainless steel products are manufactured, free iron is transferred to the surface of the material from the steel cutting, stamping and forming tools used in the manufacturing process. Free iron can also be imparted on the surface by polishing or blasting operations that utilize the same polish or blast media between both mild steel and corrosion resistant steel grades.

Free iron readily oxidizes, forming visible rust on the surface of the product. It is important to note that stainless steel is corrosion resistant but not corrosion proof. The degree of corrosion resistance of a stainless steel alloy is a function of the alloying composition, heat treatment, internal stresses and passivation treatment. An example of this phenomenon is free-machining stainless steel which has notably less corrosion resistance than stainless steel due to the higher concentration of sulfur and phosphorous that imparts the desired machinability of the grade.

As a general rule, the higher the nickel and chromium content in the alloy, the more corrosion resistance it will have. In addition, APT can meet the requirements of any company-specific nitric or citric acid stainless steel passivation methods. Inhibited passivation solutions are available to maintain bright surfaces of stainless components such as machined faces and centerless ground or stainless steel shafts.

Unfortunately, very few part prints indicate the specific method of passivation of stainless steel to be employed. Advanced Plating Technologies provides full in-house testing services to certify the performance of our stainless steel passivation including high humidity, salt spray per ASTM B, potassium ferricyanide.

Immersion bath to be controlled at pH of 1. Five testing methods to validate passivation services are provided as follows:. A table of recommended nitric acid passivation methods 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. AMS covers passivation of stainless steel to both nitric and citric method. Parts shall be immersed in an aqueous solution of 4 to 10 percent citric acid, with additional wetting agents and inhibitors as applicable. Where no type is specified, the processor may use any of the listed types that meet the requirements given within AMS The following Classes are provided for testing within AMS if no class is defined, Class 2 shall apply : Class 1 — Testing not defined or as specified by the customer, test per 4.

Various corrosion resistance tests are defined within AMS However, it is noted that certain alloys such as high carbon alloys with 0. Parts shall meet one or more of the following tests:. Table 4 within AMS provides a comprehensive summary of both nitric and citric acid methods that can be applied as a function of alloy. QQ-P does not cover citric acid passivation services.

Four active nitric acid passivation services are covered as follows four inactive methods have been withdrawn :. Four testing methods to validate passivation services are provided as follows:. Parts shall meet one or more of the following tests: Humidity Test Water Immersion Copper Sulfate Test Salt Spray Test Table 4 within AMS provides a comprehensive summary of both nitric and citric acid methods that can be applied as a function of alloy.

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ASTM A967/A967M

The standards that collectively make up the ASTM A passivation specification ensure that nitric and citric stainless steel passivation is performed properly and with quality results. The ASTM A passivation standard applies to the cleaning, passivation and testing of stainless steel parts. Chemical passivation removes free iron and other surface contaminants from stainless steel parts, improving corrosion resistance. Stainless steel passivation performed to the ASTM A standards meets these standards by passing tests that confirm its effectiveness, particularly as it pertains to removing free iron from the cold-worked surfaces.

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ASTM A967 / AMS 2700

This is the standard used by general industries to describe and control the passivation of stainless steel. Passivation is a process of making stainless steel more stainless than it would be if left alone. It is based on using an acid nitric or citric under highly controlled conditions to remove free iron particles from the surface and to help form a metal oxide layer that increases its ability to resist rusting. It is important to understand that passivation is not a coating applied to the surface; it is a process that makes the surface itself more resistant to staining or rusting. The current and previous versions describe the process and the specific parameters when using nitric acid or citric acid. Each acid has several specific combinations of concentration, temperature, and required time as well as other specific requirements.

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Passivation of Stainless Steel

Passivation of stainless steel is a process that removes free iron from the surface of a stainless component and at the same time promotes the formation of a thin, dense oxide protective barrier. APT provides both competitive high-volume commercial stainless steel passivation as well as precision medical passivation of titanium and other medical-grade alloys including cobalt chromium, MP35N and LVM, utilizing ultrasonic systems for demanding applications within the medical and dental industries. This is in stark contrast to iron oxide red rust that forms on plain carbon steel products. Iron oxide is a loose, scaly oxide that easily falls away to allow the formation of additional iron oxide, thereby perpetuating the corrosion reaction. When stainless steel products are manufactured, free iron is transferred to the surface of the material from the steel cutting, stamping and forming tools used in the manufacturing process. Free iron can also be imparted on the surface by polishing or blasting operations that utilize the same polish or blast media between both mild steel and corrosion resistant steel grades.

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ASTM A967 Standard for Nitric and Citric Stainless Steel Passivation

Historical Version s - view previous versions of standard. More A This specification covers several different types of chemical passivation treatments for stainless steel parts. The treatments are the following: immersion treatment using nitric acid solutions, immersion treatment using citric acid solution, and electrochemical treatment. Immediately after the removal from the passivating solution, the parts shall be thoroughly rinsed, using stagnant, countercurrent, or spray washes, singly or in combination, with or without a separate chemical treatment for neutralization of the passivation media. The chemical reactions of the passivating media on the surface of the stainless steel shall be stopped by rinsing of the stainless steel part, with or without a separate neutralization treatment.

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