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Prep work for Alodine

Phil

Phil

Well Known Member
I'm getting ready to begin application of alodine to the empennage of my -10.

Before I apply it, I've got a question.

When removing the vinyl strips, the soldering iron (yes it was dulled) left some light scratches on the external skin.

Before I alodine the skin, should I rub these scratches out with a 3M Maroon pad then alodine? Or should I go ahead an alodine the scratches then rub them out later and risk removing alodined material right before paint?

Thanks,
Phil
 
i used the grey ones

the red ones are really harsh. i just put a satin finish on mine and aluminum preped and the alodined. the red will work but seem to very harsh and will remove the alclad in a couple of strokes.some prefer to remove the alclad. i try to leave it intact.
 
Grey pads

Phil said:
Stupid question, but how did you use for to get the Satin Finish?
Click to expand...

UPDATE... stick with the maroon... see later post...

Phil... use the grey colored ScotchBrite pads... Scotch-Brite? Ultra Fine Hand Pad 7448

MMSB_7448.jpg


The easiest way to use it is to apply the acid etch (aka AlumiPrep) with these pads. Scrub gently, an you will get the satin finish... rub a little harder over the scratches in question. This will leave a great surface for the alodine.

gil in Tucson
 
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I use the red ones. Nothing really harsh about them. The first thing I do is wash everything wish soap and water, and the red Scotchbrite. The soap I use is Eldorado ED-500. Then I etch with Eldorado AC-12. When you rinse the etch off the metal, the water should run off cleanly. If it beads up or separates you need to etch that area again.

:)
 
Maroon

KTM520guy said:
I use the red ones. .... :)
Click to expand...
I have been told that the Red ones are about 400 grit, and the Grey ones about 600 grit, but this reference says 800 grit for the grey...

http://academic.evergreen.edu/projects/biophysics/technotes/fabric/finish.pdf

It also lists the grey 7448 as Silicon Carbide, which is not recommended for aluminum. Stick with the red 7447 (3M calls it maroon) which is aluminum oxide.

The document above is a listing of the grades... The 6444 brown is good for removing deep scratches, but it will remove the Alclad surface too...

gil in Tucson
 
If you do the wash and scrub with etch on the pads...how do you keep it out of the filler which is often used on tips (HS, VS, Elevators, etc).

Same question for applying alodine on large completed surfaces. Do you rub the alodine on and then rinse a little alater, and how do you keep it out of the filler?
 
ymmv

as said earlier, the red ones will remove the alclad easily....if that is what YOU desire then by all means use the red ones. many folks do. i simply wish to leave tha alclad intact. it is only .002 thick. but what difference would it make either way..your top coating it any way.
i rub with grey pad, then metal prep then aoldine. i wouldnt even do the grey pad but the slick alclad really resists etching. youll know youve gotten a decent etch when you dip the part and a white foam covers the component. then it turns very bright and clean aluminum. then the alodine dip leaves that nice orangeish color on it.
 
Thanks. I'll gently work it out with the maroon pad (Might even try some real fine emory cloth on some scrap too) and then Alodine it.

For the quesiton eariler about alodining a completed assembly, we're talking about washing/etching/alodining/priming each part individually right before you begin final assembly with rivets.

Phil
 
az_gila said:
It also lists the grey 7448 as Silicon Carbide, which is not recommended for aluminum. Stick with the red 7447 (3M calls it maroon) which is aluminum oxide.

gil in Tucson
Click to expand...
please show me where you saw this info. IIRC silicon is an alloy often used in aluminum. so it makes me wonder why you shouldnt use it.
 
The "bible"

cytoxin said:
please show me where you saw this info. IIRC silicon is an alloy often used in aluminum. so it makes me wonder why you shouldnt use it.
Click to expand...
Read the corrosion removal section of AC43.13-1b...

gil A
 
Jconard said:
If you do the wash and scrub with etch on the pads...how do you keep it out of the filler which is often used on tips (HS, VS, Elevators, etc).

Same question for applying alodine on large completed surfaces. Do you rub the alodine on and then rinse a little alater, and how do you keep it out of the filler?
Click to expand...

When I wash with soap I scrub kind of medium hard. Not really bearing down on it just enough to remove any dirt or dead bugs. During the etch step I scrub lightly. I don't worry about getting etch on the filler. Use lots of water and rinse well. Don't scrub the alodine. Just spray it on, wait a bit, then rinse. The amount of time you need to wait depends on the strength of your alodine. I like to make mine a little strong. Alodine on filler will not hurt anything.

Out of all the planes I have washed, I like RV's the best. Only takes an hour and a half for the whole process. Spam cans take half a day.

Hope this helps,
 
i did and it says

az_gila said:
Read the corrosion removal section of AC43.13-1b...

gil A
Click to expand...

For corrosion removal, and then says do not use on aluminum alloys except clad aluminum. he's not removing corrosion. he is using it on clad. it then goes on to say use fine or ultra fine pads.
additionaly it goes on to say in the text

as quoted from the bible pg. 6-26para.6-136 examples of removing corrosion from aluminum and aluminum alloys,

"the removal of corrosion products by hand can be accomplished by use of aluminum grit and SILICON CARBIDE ABRASSIVES, such as non woven non abrasive mat(spec mil-a-9962)abrasive cloth and paper. aluminum wool,fibre bristle brushes and pumice powder are also acceptable methods."
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/99c827db9baac81b86256b4500596c4e/$FILE/Chapter%2006.pdf
 
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It is inconsistent...

cytoxin said:
For corrosion removal, and then says do not use on aluminum alloys except clad aluminum. he's not removing corrosion and he is using it on clad. it then goes on to say use fine or ultra fine pads.
additionaly it goes on to say in the text

as quoted from the bible pg. 6-26para.6-136 examples of removing corrosion from aluminum and aluminum alloys,

"the removal of corrosion products by hand can be accomplished by use of aluminum grit and SILICON CARBIDE ABRASSIVES, such as non woven non abrasive mat(spec mil-a-9962)abrasive cloth and paper. aluminum wool,fibre bristle brushes and pumice powder are also acceptable methods."
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/99c827db9baac81b86256b4500596c4e/$FILE/Chapter%2006.pdf
Click to expand...

Yep... the "bible" contradicts itself... Table 6.1 in that section is much more specific and says no...

The section on power tools to remove corrosion only lists Aluminum oxide...

With inconsistencies, I prefer to go the safe way with is Aluminum Oxide which is OK in all interpretations.... :)

UPDATE...

This newer document from NASA says quite specifically that Silicon Carbide is OK (Section 4.2.3)... perhaps it is an old wives tale after all - or just more recent testing??

http://corrosion.ksc.nasa.gov/pubs/tm584c.pdf

gil A
 
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az_gila said:
Yep... the "bible" contradicts itself... perhaps it is an old wives tale after all - or just more recent testing??

http://corrosion.ksc.nasa.gov/pubs/tm584c.pdf

gil A
Click to expand...
added

i dont see where it contradicts itself is says ok for clad alu in the table.it says do not on alloys,

it seems that people are superstitious at times about info handed down and yet never quantified. if my dad says so and so i go the rest of my life thinking its the absolute gospel. just try telling a 19 year old student something different than his father told him. he comes back the next day "hey my dad said you were crazy." yet they still pay to go to school. :cool:

thanks for the nasa link.. ;)
 
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Table 6.1...

cytoxin said:
added

i dont see where it contradicts itself is says ok for clad alu in the table.it says do not on alloys,

.........
thanks for the nasa link.. ;)
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Well, not quite... after the do not use statement, the column for grit used is blank in the Silicpon Carbide column... no grit recommended in Table 6.1

It does not say you can use it in Table 6.1...

However the NASA link is probably much more recently published, and it's big warning is not to use carbon steel wire brushes...

gil A
 
wow thats a lot of corrosion

i bet after reading about all those different types of corrosion most would decide to prime. run duck cover. :eek:
the nasa documnet seems to be a bit more specific however and takes the guesswork out of it. i was a little concerned for a minute when i remembered doing all of my ribs with the silicon carbide grey pads. i feel better now. :)
 
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