Organic coatings filiform corrosion

D 2803 1982 (1987) Test method for filiform corrosion resistance of organic coatings... 

CORROSION, FILIFORM - Corrosion that occurs under organic coatings on metals as fine wavy hairlines. 

By using the SKP (see Sect. 5.4.2.5), it was possible to measure the local potentials underneath an organic coating in situ without the deterioration of the corroding system [178]. The mechanism of FFC consisting of an anodic reaction at the corrosion front is reflected in rather different electrode potentials around the filament s head. Whereas, for cathodic undermining, the delamination front is positively polarized with respect to the already delaminated zone and the head of the filiform filament shows a negative potential with respect to the tail (Fig. 35) [178]. Therefore, the tip can be identified as the local anode and the local cathode is situated behind the anode within the tail. 

Filiform corrosion is observed under thin organic coatings on aluminum, steel, aircraft structures exposed to humid atmosphere, beverage cans, flanges, gaskets, dis-bonded... 

Filiform corrosion is observed under thin organic coatings (typically 0.1 mm) on aluminum and steel exposed to a humid atmosphere. It has been observed in aircraft structures, beverage cans, flanges, gaskets, and weld zones [111—113]. Corrosion-resistant alloys of stainless steel, copper, and titanium are not susceptible to fihform corrosion. Metals with thin organic coatings are in contact with water from the humid atmosphere. 

D2803—09 Standard Guide for Testing Filiform Corrosion Resistance of Organic Coatings on Metal... 

G. Williams and H.N. McMurray, Poly aniline inhibition of filiform corrosion on organic coated AA2024-T3, Electrochim. Acta, 54, 4245-4252 (2009). 

Filiform corrosion under organic coatings is common on steel, aluminum, magnesium, and zinc (galvanized steel). It has also been observed under electroplated silver plate, gold plate, and under phosphate coatings. 

ASTM Standard D 2803 Standard Guide for Testing Filiform Corrosion Resistance of Organic Coatings on Metal, Anmuil Book of ASTM Standards, Vol. 6.01, ASTM International, West Conshohocken, PA, 2001. 

D 2803 Guide for testing filiform corrosion resisfance of organic coatings on metol D 2933 Test method for corrosion resistance of coated steel specimens (cyclic method) G 60 Method for conducfing cyclic humidity tests... 

Filiform Corrosion. Filiform corrosion is a special form of crevice or oxygen cell corrosion occurring beneath organic or metallic coatings on steel, zinc, aluminum, or magnesium. Filiform corrosion normally starts at small, sometimes microscopic, defects in the coating. Lacquers and "quick-dry" paints are most susceptible to the problem. 

Williams G., McMuiray H.N. (2003), Anion-exchange inhibition of filiform corrosion on organic coated AA2024-T3 aluminum alloy by hydrotalcite-like pigments , Electrochem. Solid Slate Lett., 6, B9-B11. 

Standard guide for testing filiform corrosion resistance of organic coatings on metal Standard practice for measurement of corrosion potentials of aluminium alloys... 

Williams G. and McMuixay H. N. (2004), Inhibition of Filiform Corrosion on Polymer Coated AA2024-T3 by Hydrotalcite-Like Pigments Incorporating Organic Anions , Electrochem. Solid. St, 7, B13-B15. 

The ion-exchange structure may support anionic or cationic exchange. Williams and McMurray [133] showed that release of organic anions from hydrotalcite pigments in poly(vinyl butyrate) coatings could inhibit filiform corrosion with... 

Because filiform corrosion prqngates on structural areas that are either clad or coated with organic paint, this type of material deterioration can read extensively before it is detected by airoaft maintenance personnel. In typical cases, filiform corrosion develops around fastener holes on airfimne sheet structures. Paint blistering around the rivet holes is a characteristic feature of this type of corrosion. Documented case histories of filiform corrosion of various components include the following. 

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