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John Bolding
Joined: 23 May 2006
Posts: 281
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 Posted: Tue Sep 05, 2006 4:57 am Post subject: Cleaning aluminum, aerobatics |
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OK guys , I know you should have only one subject per post but I prefer lurking to posting so I like to get it over with in a hurry.
Cleaning aluminum:
I REALLY hope I don't hurt anyone's feelings here and that is certainly not my intent.
Over the yrs I have read hundreds of times on this list and several others that I monitor about wiping down the alum. part with some solvent( MEK, acetone and lacquer thinner being the most common)as the final prep for painting.
My career in the paint spray equipment industry for 35 yrs put me in the middle of hundreds of paint film examinations to determine cause of failure. Normally the paint supplier or part washer guy was the lead role in these goat ropings but the equipment guy HAD to show up or he was automatically the cause, kinda like missing a meeting when your EAA Chapter holds elections, you WILL be an office holder if you miss.
Some paints are more tolerant than others of a not perfectly clean surface, waterborne materials and powder are the least tolerant (in my limited experience anyway).
Solvent is a poor choice for cleaning.
Imagine coming in from the shop for lunch and grabbing a can of MEK and a rag and cleaning your greasy hands with it, no water, just a rag wet with solvent. You succeed in getting them to look a little better but you HAVEN'T taken all the dirt/ grease off, just moved it around in smaller concentrations. Follow up with a clean rag and more solvent reduces the concentrations but .... you get the picture.
Now if you agitate a surfactant(soap) into the part to be cleaned,(your hands)using water and when you get all the junk floating (paint guys called it "suspended" 'cause they made a lot of money and wanted to impress the customer) and introduce a rinse(LOTS of water to flood the surface) to remove it ,you generally get a squeaky clean surface first rattle out of the box. Repeat as necessary.
What I learned from all these dog and pony shows was that the oils you are trying to remove can be effective (with some coatings) down to the molecular level at causing adhesion problems down the road. Ever been at a boat dock and noticed the oil sheen on the water, it's only a few molecules thick. You CAN'T be assured you get it ALL off unless you wash and rinse.
Now comes the part where 83 guys that have been painting since before birth tell me that I'm all wet and they never had a problem in wiping down a car with a rag and solvent. Save it, I heard it a thousand times. What impressed ME was the chemist who brought along a BIG microscope to one of these meetings and SHOWED me oil between the substrate and paint film where it had peeled off. Takes a lot of work to build an airplane, prep it properly.
Aerobatics:
First airplane I built was an RV3 about a hundred yrs ago (12th RV to fly) and at that time the test stage included strapping on a parachute and subjecting the airframe to LIMIT loads. In the case of the "3" it was 6 G's. Not comfortable and not fun really, but it was part of the package so you did it. I always thought it was unnecessary as I could do a roll with a 1/2 G and a loop using a little less than 2.
Then came the time I fell out of the top of a loop that I was trying to make too big and pulled almost 6 G in the botched recovery, Oh THAT'S why you do that "un-necessary" testing!! Nuff said.
LOW&SLOW John Bolding
[quote][b]
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Geoff Heap
Joined: 12 Jan 2006
Posts: 266
Location: Lindenwold, New Jersey
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| Posted: Thu Sep 07, 2006 6:11 pm Post subject: Re: Cleaning aluminum, aerobatics |
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IMPRESSIVE
do not archive...........Geoff
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Eddie G.
Joined: 03 Nov 2006
Posts: 15
Location: Los Angeles, CA
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| Posted: Wed Jan 31, 2007 1:55 pm Post subject: Re: Cleaning aluminum, aerobatics |
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Hi,
I was searching the archives for a good alternative to cleaning parts before priming (indoors) and found John Bolding's writeup below.
So, what is a good, safe cleaner that I can use indoor without risking exposure to carcinogen chemicals and without causing chemical reactions on the aluminum parts? I am currently building my rudder in a corner of my living room which has turned out to be a nice comfortable work place. Am planning on brushing AFS primer/sealer on the contact points and leaving the rest of the surfaces untreated. I am also thinking of soaking the rivet heads in a thinned solution of primer/sealer before riviting.
Should I consider using soap and distilled water followed by rubbing alcohol?
Thanx...Eddie
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[quote="John Bolding"]OK guys , I know you should have only one subject per post but I prefer lurking to posting so I like to get it over with in a hurry.
Cleaning aluminum:
I REALLY hope I don't hurt anyone's feelings here and that is certainly not my intent.
Over the yrs I have read hundreds of times on this list and several others that I monitor about wiping down the alum. part with some solvent( MEK, acetone and lacquer thinner being the most common)as the final prep for painting.
My career in the paint spray equipment industry for 35 yrs put me in the middle of hundreds of paint film examinations to determine cause of failure. Normally the paint supplier or part washer guy was the lead role in these goat ropings but the equipment guy HAD to show up or he was automatically the cause, kinda like missing a meeting when your EAA Chapter holds elections, you WILL be an office holder if you miss.
Some paints are more tolerant than others of a not perfectly clean surface, waterborne materials and powder are the least tolerant (in my limited experience anyway).
Solvent is a poor choice for cleaning.
Imagine coming in from the shop for lunch and grabbing a can of MEK and a rag and cleaning your greasy hands with it, no water, just a rag wet with solvent. You succeed in getting them to look a little better but you HAVEN'T taken all the dirt/ grease off, just moved it around in smaller concentrations. Follow up with a clean rag and more solvent reduces the concentrations but .... you get the picture.
Now if you agitate a surfactant(soap) into the part to be cleaned,(your hands)using water and when you get all the junk floating (paint guys called it "suspended" 'cause they made a lot of money and wanted to impress the customer) and introduce a rinse(LOTS of water to flood the surface) to remove it ,you generally get a squeaky clean surface first rattle out of the box. Repeat as necessary.
What I learned from all these dog and pony shows was that the oils you are trying to remove can be effective (with some coatings) down to the molecular level at causing adhesion problems down the road. Ever been at a boat dock and noticed the oil sheen on the water, it's only a few molecules thick. You CAN'T be assured you get it ALL off unless you wash and rinse.
Now comes the part where 83 guys that have been painting since before birth tell me that I'm all wet and they never had a problem in wiping down a car with a rag and solvent. Save it, I heard it a thousand times. What impressed ME was the chemist who brought along a BIG microscope to one of these meetings and SHOWED me oil between the substrate and paint film where it had peeled off. Takes a lot of work to build an airplane, prep it properly.
LOW&SLOW John Bolding
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