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Is this corrosion??

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william(at)gbta.net
Guest

Posted: Thu Jan 15, 2009 9:03 pm Post subject: Is this corrosion??

Finally got around to wings and found what looks  like corrosion on some of the W-1025A flap hinge brackets.  If it's  corrosion do I need to worry about it and replace the parts or clean and prime  them somehow???  I'll send pics to Vans also to see what they  say.

  

 Thanks,

 bill[img]cid:AA318B05B7A4448AA55D75FB990EEE86(at)Britton[/img]

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ricksked(at)embarqmail.co
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Posted: Fri Jan 16, 2009 8:17 am Post subject: Is this corrosion??

Bill, 

  

It looks like corrosion but not on a large scale, I suspect that there may have been some corrosive chemial stored nearby in the garage/workshop? It would take water quite awhile to develop the pitting I see. Pool chemicals, fertilizer, pesticides etc in a oxygen/moisture enviromet will create an acidic atmoshphere that will accelerate the process. Just my $1.25 worth, heres some info from the U.S. Army's corrosion identification and abatement course. I did'nt include all the forms just the ones that would be applicable to bare metals. Filliform is another fun topic. 

  

Rick Sked 

40185 

  

Uniform surface corrosion  

Uniform surface corrosion results from a direct chemical attack on a metal surface and involves only the metal surface. On a polished surface, this type of corrosion is first seen as a general dulling or etching of the surface and if the attack is allowed to continue, the surface becomes rough and possibly frosted in appearance. This type of corrosion appears uniform because the anodes and cathodes are very small and constantly shift from one area of the surface to another. An example is the etching of metals by acids. The discoloration or general dulling of metal created by exposure to elevated temperatures is not considered to be uniform surface corrosion. 

  

Pitting 

The most common corrosion of aluminum and magnesium alloys is pitting. It is first noticeable as a white or gray powdery deposit, similar to dust, which blotches the surface. When the deposit is cleaned away, tiny pits or holes can be seen in the surface. Pitting corrosion may also occur in other metal types or alloys. The combination of small active anodes to large passive cathodes causes severe pitting. 

  

Galvanic Galvanic corrosion occurs when different metals are in contact with each other and an electrolyte, such as salt water, is present. It is usually recognizable by the presence of a buildup of corrosion at the joint between the metals. Two dissimilar metals joined together form a galvanic couple if moisture and contamination are present 

  

Light corrosion  

Where the condition of the metal is characterized by discoloration and pitting to a depth of 0.001 INCH (1 mil). This type of damage can normally be removed by light hand sanding.   

  

Moderate corrosion 

Where the condition of the metal is characterized by blisters, evidence of scaling, of the coating or paint system, intergranular corrosion, and pitting to a depth of 0.001 INCH (1 mil) to 0.010 INCH (10 mils). This type of damage shall be removed by extensive hand sanding, light mechanical sanding, or by deoxidizing with a corrosion removing compound. 

  

Severe corrosion 

Where the condition of the metal is characterized by blistering, evidence of scaling, flaking of the coating or paint system, intergranular corrosion, and pitting to a depth greater than 0.010 INCH (10 mills). This type of damage shall be removed by extensive mechanical sanding, grinding, or by deoxidizing with a corrosion removing compound 

  

Enviromental factors 

  

Moisture 

Moisture is present in the air and often contains contaminants such as chlorides, sulfates, and nitrates. Condensed moisture after it evaporates, will leave its contaminants on surfaces of the aircraft. Accumulations of moisture may result from cycles of warming and cooling, and drawn along poor bond lines by capillary action. 

  

Temperature/Climate 

Generally, corrosion will increase as temperatures rise, but a moderate increase may reduce corrosion by prevent- ing condensation. Temperatures above 104 Â°F (40 Â°C) will inhibit mold and bacteria growth. Temperatures held at the lower end of the range will generally reduce the rate of corrosion. Warm, moist air, normally found in tropical climates tends to accelerate corrosion while cold, dry air normally found in artic climates tends to reduce corrosion rates. Corrosion  does  not  occur  in  very  dry  conditions.  Certain  areas  within  an  aircraft,  such  as  the  cockpit  and  air conditioned equipment bays, may be subjected to climatic dry air that has been cooled by air conditioners. This reduces its ability to hold moisture, and when ducted into interior area of the aircraft, can release sufficient moisture to accelerate corrosion.  

  

Salt 

Salt dissolved in water forms a strong electrolyte. Normal winds carry 10 to 100 pounds of sea salt per cubic mile of air. Since dissolved salts are strong electrolytes, salt water environments are highly corrosive to aircraft. d.   Ozone Ozone is an active form or oxygen which is formed naturally during thunderstorms, by arcing in electrical devices, and by photochemical reactions in smog. When ozone is absorbed by electrolyte solutions in contact with metals, it increases the rate of corrosion. 



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jeff(at)westcottpress.com
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Posted: Fri Jan 16, 2009 8:49 am Post subject: Is this corrosion??

Bill,



My suggestion is to take a scotchbrite pad to it until whatever that is is gone and the surface is smooth.  Clean it up with some coleman fuel or acetone and shoot it with a bit of primer.  Unless that runs deep in to the part, I don't think you've got a problem.

Jeff Carpenter

40304

(spending a lot of time on the phone with Stein these days... structure is almost done, control systems are in... but big money between me and the finish line)



On Jan 15, 2009, at 8:57 PM, Bill and Tami Britton wrote:

[quote]Finally got around to wings and found what looks like corrosion on some of the W-1025A flap hinge brackets.  If it's corrosion do I need to worry about it and replace the parts or clean and prime them somehow???  I'll send pics to Vans also to see what they say.

 

Thanks,

bill<AA318B05B7A4448AA55D75FB990EEE86>

[b]

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william(at)gbta.net
Guest

Posted: Fri Jan 16, 2009 9:05 am Post subject: Is this corrosion??

Thanks guys.  Ken from Vans says to clean it  up and prime it.  It was mentioned that I must store chemicals in the  garage to create a somewhat "acidic"environment but in reality I don't store any  chemicals in there.  The blue "wrap" from vans was peeled off where the  "corrosion" took place.

  

 Thanks,

 Bill

 [quote]   ---

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planesmith(at)hotmail.com
Guest

Posted: Fri Jan 16, 2009 10:02 am Post subject: Is this corrosion??

Bill C

  

 If you have Alumiprep and alodine these are good to use. The etching and conversion coat process will stop any corrosion that may be missed by the Scotchbrite.

  

 Vern Smith (finishing #324) 

   

 From: william(at)gbta.net

To: rv10-list(at)matronics.com

Subject: Re: RV10-List: Is this corrosion??

Date: Fri C 16 Jan 2009 11:04:39 -0600

    Thanks guys.  Ken from Vans says to clean it up and prime it.  It was mentioned that I must store chemicals in the garage to create a somewhat "acidic"environment but in reality I don't store any chemicals in there.  The blue "wrap" from vans was peeled off where the "corrosion" took place.

  

 Thanks C

 Bill

 [quote] ---

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Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Fri Jan 16, 2009 8:50 pm Post subject: Is this corrosion??

Have you cleaned with acetone? Frequently the blue vinyl leaves adhesive 

behind that looks like white residue. If not adhesive, probably fine 

scotchbrite will clean it right up.



Bill and Tami Britton wrote:

[quote] Thanks guys.  Ken from Vans says to clean it up and prime it.  It was 

 mentioned that I must store chemicals in the garage to create a somewhat 

 "acidic"environment but in reality I don't store any chemicals in 

 there.  The blue "wrap" from vans was peeled off where the "corrosion" 

 took place.

  

 Thanks,

 Bill

 

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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

william(at)gbta.net
Guest

Posted: Fri Jan 16, 2009 9:08 pm Post subject: Is this corrosion??

Haven't tried anything yet but will in the next day or two.  Too busy 

working on spars and ribs!!!



Bill

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