Carlos Sa
Joined: 13 Jan 2006
Posts: 96
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 Posted: Fri Feb 10, 2006 7:55 am Post subject: Filiform corrosion (was "The attack of the killer scotchbrit |
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There are several web pages discussing filiform corrosion, and none seem to indicate previous
contact with you-know-what.
Here is one extract from a NASA site:
**********
"This type of corrosion occurs under painted or plated surfaces when moisture permeates the
coating. Lacquers and "quick-dry" paints are most susceptible to the problem. Their use should be
avoided unless absence of an adverse effect has been proven by field experience. Where a coating
is required, it should exhibit low water vapor transmission characteristics and excellent
adhesion. Zinc-rich coatings should also be considered for coating carbon steel because of their
cathodic protection quality."
**********
Nanjing University:
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"Filiform corrosion, sometimes also called "wormtrack corrosion", is a very characteristic type
of (oxygen concentration cell) corrosion that occurs under some coatings in the form of randomly
distributed threadlike filaments.
It most commonly occurs on aluminum alloys coated with an organic coating, but other examples
exist (e.g., on nickel alloys covered with a thick oxide layer in high-temperature chloride
solutions).
The filaments grow along the metal / coating interface at typical rates up to 1mm/day (0.04
in/d). The moving end of the filament is called the "head", and the remainder of the track is
called the "tail"."
**********
Some URLs for your reference:
NASA: http://corrosion.ksc.nasa.gov/html/filicor.htm
Florida State University: http://www.chem.fsu.edu/editors/STEINBOCK/projects/ffc/ffc.htm
Department of Mechanical Engineering, Nanjing University of Chemical Technology:
http://httd.njuct.edu.cn/MatWeb/corrosie/c_fil.htm
There are many more hits, if you care to search.
Cheers
Carlos
--- "Weston, Jim" <Jim.Weston(at)delta.com> a crit :
| Quote: |
I looked at your pictures. That is what is called filliform corrosion.
The best way to stop it is to lightly sand the area with some 400 grit
wet/dry sandpaper then spray it with ACF50 or a similar product that is
meant for the treatment of corrosion. Aircraft Spruce sells the ACF50
is spray cans or by the gallon to treat an entire aircraft.
By the way, filliform corrosion once started will continue to spread
like roots from a tree. Don't use the part until you've killed the
corrosion.
Jim Weston
Concord, Ga.
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Lche-vitrine ou lche-cran ?
magasinage.yahoo.ca
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Montreal, Canada |
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