Passivation is the process of making a material "passive" in relation to another material prior to using the materials together. For example, prior to storing hydrogen peroxide in an aluminium container, the container can be passivated by rinsing it with a dilute solution of nitric acid and peroxide alternating with deionized water. The nitric acid and peroxide oxidizes and dissolves any impurities on the inner surface of the container, and the deionized water rinses away the acid and oxidized impurities. Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... The chemical compound nitric acid (HNO3), also known as aqua fortis and spirit of nitre, is an aqueous solution of hydrogen nitrate (anhydrous nitric acid). ... Deionized water (DI water or de-ionized water; also spelled deionised water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. ... To oxidize an element or a compound is to increase its oxidation number. ...

In the context of corrosion, passivation is the spontaneous formation of a hard non-reactive surface film that inhibits further corrosion. This layer is usually an oxide or nitride that is a few atoms thick. Corrosion is deterioration of essential properties in a material due to reactions with its surroundings. ...

Mechanismes of passivation

Under normal conditions of pH and oxygen concentration, passivation is seen in such materials as aluminium, iron, magnesium, zinc, magnesium copper, stainless steel, titanium, and silicon. Ordinary steel can form a passivating layer in alkali environments, as rebar does in concrete. The conditions necessary for passivation are recorded in Pourbaix diagrams. The correct title of this article is . ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic pinkish red Atomic mass 63. ... The 630 foot high, stainless-clad (type 304) Gateway Arch defines St. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Atomic mass 47. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance as coarse powder, dark gray with bluish tinge Atomic mass 28. ... The old steel cable of a colliery winding tower Steel is an alloy whose major component is iron, with carbon content between 0. ... For other uses of the word alkali see Alkali (disambiguation). ... Rebar is common steel reinforcing bar, an important component of reinforced concrete and reinforced masonry structures. ... Concrete being poured, raked and vibrated into place in residential construction in Toronto, Ontario, Canada. ... A Pourbaix diagram, also known as a potential/pH diagram, maps out possible stable (equilibrium) phases of an aqueous electrochemical system. ...

Some corrosion inhibitors help the formation of a passivation layer on the surface of the metals to which they are applied. Corrosion inhibitor - Wikipedia /**/ @import /w/skins-1. ...

Electrochemical passivation processes

Some compounds, dissolving in solutions (chromates, molibdenates) formed non-reactive and low solubile films on metal surface. A sample of ammonium dichromate Chromates and dichromates are salts of chromic acid and dichromic acid, respectively. ...

Passivation of specific materials

Aluminum may be protected from oxidation by anodizing and/or allodizing (sometimes called Alodining), or any of an assortment of similar processes. (See terminology, below.) In addition, stacked passivation techniques are often used for protecting aluminum. For example, chromating is often used as a sealant to a previously-anodized surface, to increase resistance to salt-water exposure of aluminum parts by nearly a factor of 2 versus simply relying on anodizing. Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... The iPod mini has an anodised aluminium surface, and comes in many colours Anodizing or Anodising is a process used to protect aluminium from abrasion and corrosion and to allow it to be dyed in a wide range of colors. ...

Iron based (ferrous) materials, including steel, may be somewhat protected by promoting oxidation ("rust") and then converting the oxidation to a metalophosphate by using phosphoric acid and further protected by surface coating. As the uncoated surface is water-soluble a preferred method is to form manganese or zinc compounds by a process commonly known as Parkerizing. Older, less-effective but chemically-similar electrochemical conversion coatings included bluing, also known as black oxide. General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... The old steel cable of a colliery winding tower Steel is an alloy whose major component is iron, with carbon content between 0. ... Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is an inorganic mineral acid having the chemical formula H3PO4. ... General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Atomic mass 54. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... Parkerizing (sometimes called phosphating) is a method of protecting steel surfaces from corrosion and thus increasing their durability. ... Bluing is a passivation process in which steel is partially protected against rust, and is named after the blue-black appearance of the resulting protective finish. ...

Nickel can be used for handling elemental fluorine, thanks to a passivation layer of nickel fluoride. General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic and silvery with a gold tinge Atomic mass 58. ... General Name, Symbol, Number fluorine, F, 9 Chemical series halogens Group, Period, Block 17, 2, p Appearance Yellowish brown gas Atomic mass 18. ...

Terminology for assorted passivation processes

Bluing, also known as black oxide, and sometimes called browning when used in reference to historical processes dating from the 18th Century, is a passivation coating for the surfaces of iron and steel objects. It is one of the oldest passivation processes. Bluing is a passivation process in which steel is partially protected against rust, and is named after the blue-black appearance of the resulting protective finish. ...

Newer, proprietary (and/or trademarked) processes for conversion coatings include Parkerized for passivating steel, dating to roughly 1912, and Alodine for passivating aluminum; both are trademarked processes and are now owned by Henkle Surface Technologies. [1],[2] Parkerizing (sometimes called phosphating) is a method of protecting steel surfaces from corrosion and thus increasing their durability. ...

Chem film is any generic chromate conversion coating used to passivate aluminium. One such example is U.S. Patent 5304257 . In general, however, chromate can also mean any of several chromate conversion coatings that can be applied to a much wider range of metals and alloys than just to aluminum. In recent years, chromate coatings have become less popular due to concerns over environmental pollution from using such processes. Zinc chromate conversion coating on small steel parts. ...

Iridite is another trademarked name of a whole family of proprietary conversion coatings owned by MacDermid. A competing conversion coating used on aluminum, that somewhat ameleriorates the environmental pollution concerns caused by chromate coatings, it often appears as a slightly yellowish coating, of roughly the same color as a yellow highlighting pen used to mark text on paper. [3]

Rationale for passivating aluminum

Aluminum naturally forms an oxide almost immediately that protects it from further oxidation in many environments. Unfortunately, this naturally-occurring oxide provides no protection during exposure to any saltwater spray environments, such as occurs in areas near bodies of saltwater. In such coastal environments, unprotected aluminum will turn white, corrode, and largely vanish over periods of exposure as short as a few years. The only way to prevent this from occurring is to use a more robust conversion coating on aluminum surfaces that will not be affected by the saltwater atmosphere. Alodine, Iridite, and chem film coatings can provide varying amounts of protection for aluminum surfaces.

Further reading

ASTM A967 provides advice for the passivation of stainless steel parts. Chromate Conversion Coat (Chemical Film) Per MIL-C-5541 For Aluminum and Aluminum Alloy Parts ASTM International is an international voluntary standards organization that develops and produces technical standards for materials, products, systems and services. ...

References

A standard overview on black oxide coatings is provided in MIL-HDBK-205, Phosphate & Black Oxide Coating of Ferrous Metals. Many of the specifics of Black Oxide coatings may be found in MIL-DTL-13924 (formerly MIL-C-13924). This Mil-Spec document additionally identifies various classes of Black Oxide coatings, for use in a variety of purposes for protecting ferrous metals against rust.

• Budinski, Kenneth G. (1988), Surface Engineering for Wear Resistance, Englewood Cliffs, New Jersey: Prentice Hall
• Brimi, Marjorie A. (1965), Electrofinishing, New York, New York: American Elsevier Publishing Company, Inc..

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