Aluminum corrosion, inhibited

Corrosion-inhibiting primers based on this technology have been in continuous service since they were first utilized with nitrile epoxies in the late 1960s. These inhibitors function by passivating the aluminum. In this process, water permeating the adhesive bondline carries a certain amount of inhibitor to the oxide surface. 

Although azoles are commonly thought of as only yellow metal inhibitors, they are, in fact, used for corrosion inhibition in a wider range of metals such as steel and aluminum. They also are often incorporated in molybdate-based programs to both provide some synergism and reduce the level of molybdate required. Azoles also are employed in many types of organic-based formulations, where they improve the overall protection of steel and reduce the risk of corrosion of yellow metals due to the corrosive action of some common phosphonates. 

In military aerospace vehicles, the service conditions are most severe for paints. One way to increase protecion of aluminum in acidic marine environments is to enhance the corrosion inhibiting ability of the inorganic coating. This paper describes the results of such an effort. A new coating which not only inhibits the attacic of chloride ions but also that of the acidic environments such cis SO2 has been developed. 

The mechanism of developing corrosion protective properties in an inorganic coating principally consists of forming insoluble oxides on the netal surface. Additionally, oxides must have certain corrosion inhibition (redox) properties which can protect the nnetal substrate from corrosive species like Cl and 804 . In the case of chromate conversion coating, OCC, the oxides of aluminum and chromium have been responsible for their corrosion inhibitive properties which were derived from their soluble and insoluble portions of the... 

Zinc chromate (ZnCr04), also known as zinc yellow (with the approximate formula 4Zn0K204Cr03-3H20), is used as a pigment because of its excellent corrosion-inhibiting effect both in mixed paints and as a priming coat for steel and aluminum. 

Kendig MW Buchheit RG, Corrosion inhibition of aluminum and aluminum alloys by soluble chromates, chromate coatings, and chromate-free coatings, Corrosion, 2003, 59, 379-400. 

E 866 Specification for Corrosion Inhibiting Adhesive Primer for Aluminum Alloys to be Adhesively Bonded in Honeycomb Shelter Panels... 

Using the HSAB principle, one can rationalize the corrosion inhibition of iron and aluminum by phosphate in which iron phosphate and aluminum phosphate are produced. Ferric and Al3+ are hard acids, and they react with phosphate, a hard inhibitor and give corrosion protection. Corrosion inhibition of Cu2+ and Zn2+ by amines can be rationalized by the formation of amine complexes of Cu2+ and Zn2+, and this is in accord with the principle that Cu2+ and Zn2+ are borderline acids reacting with amines which belong to borderline inhibitors. Corrosion protection of copper (soft acid) by mercapto-benzothiazole (soft inhibitor) is also in keeping with the HSAB principle. 

Corrosion inhibitors such as chromates, silicates, polyphosphates, nitrites, nitrates, borates and mercaptobenzothiazole have been used in corrosion inhibition of aluminum and its alloys.45... 

Lead chromate pigments are mainly used as corrosion inhibitive pigments. These pigments are of low opacity and can be combined with higher opacity pigments for use in primers. Zinc chromate, also an anti-corrosion pigment, is used in metal pretreatments such as wash primer, which also promotes adhesion to aluminum and steel. 

U.S. 5624892 (1997) [128] Angevaare et al. (Lever Bros.) Aluminum sequestrant Inhibits lead corrosion... 

The empiricism that appears to follow the corrosion engineer arises from the multi-factor, multi-component situations which are present within all common articles of commerce, be they made from iron, aluminum, or more exotic material combinations. The variables are continually interacting in increasingly complex ways so we can become engrossed for even a lifetime with just one problem in performance such as airfoil stress corrosion cracking, boiler feed water stabilizations, or corrosion inhibiting paints, and many more. But does this mean the work lacks for glamour and excitement ... 

One apparent contradiction that has not been resolved is that some microorganisms in biofilms can cause locahzed corrosion and others inhibit generalized corrosion. To further complicate matters, the same organisms and mechanisms to which MIC has been attributed can also reportedly inhibit corrosion. For example, strains of Pseudomonas and Serratia are reported to increase the corrosion rate of iron and nickel compared to sterile conditions [103], but can have a protective effect on some metals under certain circumstances [104, 105]. Videla and Guiamet [106] found a protective action of S. marcescens on aluminum. Metal-binding by extracellular polymers has been reported as a mechanism for both MIC [107] and for corrosion inhibition [86]. 

Uses Adhesion promoter for baked alkyds, polyesters, acrylics, and lacquers onto metal substrates corrosion-inhibiting pretreatment or base coating for galvanized steel and aluminum suitable for food-contact coatings... 

Corrosion inhibition of chemically and electrochemically synthesized coatings of PANI, poly (o-methoxyaniline), and their copolymers on stainless steel and on aluminum alloy (6061-T6) was evaluated by immersion in 3% NaCl (steel) and 0.1 M NaCl (A1 alloy). These authors concluded from polarization studies that protection involved an anodic protection mechanism [206]. 

Ogurtsov, N.A., et al. 2004. Corrosion inhibition of aluminum alloy in chloride mediums by undoped and doped forms of polyaniline. Synth Met 143 (1) 43. 

Kinlen, RJ. 2005. Electroactive polymers and Smart coatings for corrosion inhibition of aluminum alloys. In Smart Coatings 2005, Orlando, FL. 

Yang, S.C., et al. 2003. Electroactive polymer for corrosion inhibition of aluminum alloys, in Electroactive polymers for corrosion control, eds. P. Zarras, J.D. Stenger-Smith and Y. Wei, 196. Washington, DC American Chemical Society. 

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