What is filiform corrosion?
What is filiform corrosion?
Abstract. Filiform corrosion is a form of corrosion specific to painted steel, aluminium and magnesium surfaces. It results in a detachment of the coating from its metallic support, which is caused by the surface corrosion of the underlying metal at the metal/coating interface.
How is filiform corrosion caused?
4 Filiform corrosion. As mentioned above, filiform corrosion is a particular form of crevice corrosion. This type of corrosion typically occurs on coated surfaces when moisture or a corrosive solution penetrates through the defective coatings. It is caused by active galvanic cells across the metal surface.
How is filiform corrosion detected?
Filiform corrosion can be visually recognized without using a microscopy. Filiform corrosion has been observed on surfaces of coated steel, magnesium, and aluminum with thin coatings of tin, silver, gold, phosphate, enamel, and lacquer. Filiform corrosion has also been observed on paper-backed aluminum foils.
Why is crevice corrosion a problem?
In general, crevice corrosion is of greatest concern for materials which are normally passive metals, like stainless steel or aluminum. Crevice corrosion is extremely dangerous because it is localized and can lead to component failure while the overall material loss is minimal.
How is filiform corrosion treated?
To repair the effect requires sanding and the application of a new layer of coating. To prevent filiform corrosion, proper surface pretreatment is required. The most important factor for the coating is to have very strong adhesion to the substrate to prevent the corrosion from starting.
Where is filiform corrosion most likely to occur?
Where is filiform corrosion most likely to occur on an aircraft? Under a dense coating of topcoat enamel such as polyurethane. Filiform corrosion is caused by improperly cured primer.
How do you fix filiform corrosion?
Filiform corrosion typically occurs in humid / warm environments and is noticeably more common in coastal and industrial areas. Painted aluminum parts with filiform corrosion can be repaired by removal of the coatings and corrosion by sanding, followed by refinishing with OEM recommended refinish materials.
What is the principle of crevice corrosion?
Crevice corrosion is initiated by a difference in concentration of some chemical constituents, usually oxygen, which set up an electrochemical concentration cell (differential aeration cell in the case of oxygen). Outside of the crevice (the cathode), the oxygen content and the pH are higher – but chlorides are lower.
How can you tell if a crevice is corroded?
Some visible signs of crevice corrosion include:
- Localized discoloration of the paint covering an area at or near where metals are joined.
- Localized flaking of protective coatings at or near the corrosion site.
- Localized flaking of one of the metals at the area where two metals are joined.
How do you fix filiform corrosion on an Airstream?
There’s really no fix for filiform corrosion that has already happened. Since the corrosion is beneath the clearcoat, you can’t remove it without removing the clearcoat first—which tends to cause an uglier problem.
What type of corrosion usually occur on piano hinges?
Piano-type hinges are prime spots for corrosion due to the dissimilar metal contact between the steel pin and aluminum hinge. They are also natural traps for dirt, salt, and moisture.
What is filiform corrosion and what does it mean?
What Does Filiform Corrosion Mean? Filiform, or underfilm corrosion is a type of corrosion that is commonly known as “localized” and is normally linked to magnesium and aluminum alloys that utilize an organic form of coating. However, it can also occur on other coated metals such as steel, iron and zinc.
What is 153 4 filiform corrosion?
15.3.4 Filiform corrosion. As mentioned above, filiform corrosion is a particular form of crevice corrosion. This type of corrosion typically occurs on coated surfaces when moisture or a corrosive solution penetrates through the defective coatings. It is caused by active galvanic cells across the metal surface.
How do you prevent filiform corrosion?
This type of deformed layer-induced filiform corrosion can be prevented by acid or alkaline etching to remove the deformed surface layer, by reducing the manganese level in the alloy or by heat treatment to precipitate the manganese from solid solution before rolling.
What does filiform mean in anatomy?
Filiform, thread or filament like, can refer to: Filiform, a common term used in botany to describe the shape of plant parts, such as leaf shape. Filiform, or filiform catheter, a medical device whose component parts or segments are all cylindrical and more or less uniform in size. Filiform papilla on the tongue.
