7.13.7.3 Filiform Corrosion
Metals with semipermeable coatings or films may undergo at ype of
corrosion,r esulting in numerous meandering threadlike filaments of
corrosion beneath the coatings or films. Conditions that promote this type
of corrosionare:
1. Highrelative humidity (60–95%atroom temperature).
2. The coating is permeable to water.
3. Contaminants (salts, etc.) are present on or in the coating or at the
coating-substrate interface.
H 2 OH 2 O
H 2 O
Corrosion initiation
Blocking of pore
anodic
Cathodic delamination
C
C
H 2 O
H 2 O
O 2
H 2 OO 2
H 2 OH 2 OH 2 O
O 2
O 2
O 2
O 2
FIGURE 7.25
Blister initiation and propagation under adefective coating (cathodic delamination).
Coatings
481
CAT8247—CHAPTER 7—17/10/2006—15:04—TRGANESH—XMLM ODEL B–pp. 403–485
Metals with semipermeable coatings or films may undergo at ype of
corrosion,r esulting in numerous meandering threadlike filaments of
corrosion beneath the coatings or films. Conditions that promote this type
of corrosionare:
1. Highrelative humidity (60–95%atroom temperature).
2. The coating is permeable to water.
3. Contaminants (salts, etc.) are present on or in the coating or at the
coating-substrate interface.
H 2 OH 2 O
H 2 O
Corrosion initiation
Blocking of pore
anodic
Cathodic delamination
C
C
H 2 O
H 2 O
O 2
H 2 OO 2
H 2 OH 2 OH 2 O
O 2
O 2
O 2
O 2
FIGURE 7.25
Blister initiation and propagation under adefective coating (cathodic delamination).
Coatings
481
CAT8247—CHAPTER 7—17/10/2006—15:04—TRGANESH—XMLM ODEL B–pp. 403–485