Technically, the QUALICOAT standard is more robust as it specifies minimum etch requirements within the pretreatment process and a finished powder coated surface test for filiform corrosion
resistance, which the BS EN 12206-1 does not require.
Assessment of degree of blistering, rusting and cracking was done by time to time according to standard ISO 4628 (Part 2, 3, 4)  while the degree of filiform corrosion
was assessed by ISO 4628 (Part 10)  at the end of exposure.
The recommended anticorrosive primer from Company A was used as the primer for both topcoats in the salt spray and filiform corrosion
tests, following the procedure in MIL-PRF-23377K.
The common corrosion types are mainly galvanic corrosion, pitting corrosion, filiform corrosion
and stress corrosion of these.
* 10 Assessment of degree of filiform corrosion
. Shock and Vibration Methods for the calibration of vibration and shock transducers.
(23.) Romano, A-P, Fedel, M, Deflorian, F, Olivier, M-G, "Silane Sol-Gel Film as Pretreatment for Improvement of Barrier Properties and Filiform Corrosion
Resistance of 6016 Aluminium Alloy Covered by Cataphoretic Coating." Prog.
Polymeric coatings on aluminum are generally subjected to filiform corrosion
which usually starts at cut edges .
Nisancioglu, "Filiform corrosion
of aluminium sheet.
Persson, "The role of chromate conversion coating in the filiform corrosion
of coated aluminum alloys," Journal of the Electrochemical Society, vol.
Table 1--Corrosion types for metals in water storage General Corrosion Pitting Corrosion Crevice Corrosion Galvanic Corrosion Intergranular Corrosion Stress Corrosion Cracking End-Grain Attack Erosion-Corrosion Blister Formation (Filiform Corrosion
) Microbial Corrosion Sediment-Induced Corrosion Table 2.
An important degradation mechanism of organic-coated metals exposed to humid atmospheres is filiform corrosion
. Although filiform corrosion
is usually observed on organic-coated aluminum parts, (299-301) it has also been observed on magnesium and cold-rolled steel.
"In salt spray and filiform corrosion
testing, metal surfaces protected by new Desoprime HS CA 7502 high-solids exterior epoxy primer showed the same corrosion resistance as those coated with chromated primers," Schoeder said.