Michael Burbidge
Well Known Member
Does scuffing the surface of alclad aluminum with red scoth-brite pad remove the alclad?
Do scratches in the alclad need to be buffed out?
Do scratches in the alclad need to be buffed out?
i think a moderate scrubbing will remove it with the red pad...others argue this TEHO. you can feel the pad increase in resistance when it breaks through and seems to be a different color. the alloy seems very hard compared to the clad. the clad provides no structual strength at all. so if it didnt go deeper than the clad than i would say it does not need to be polished.YMMV
This has been debated before, but going over alclad until you've uniformly knocked off the shine will not remove the cladding. It takes a lot of scrubbing to get through it. I'm not saying you can't do it, but it would be pretty hard to do it inadvertantly. Others will disagree, but I've actually tried it with a timer and a micrometer. It takes minutes, not seconds.
Yes, using a Scotchbrite pad removes the Alclad, ...
Alcad is an extremely thin protective of 99% pure aluminum. Certainly scuffing the alclad surface with virtually anything including your fingernail will easily remove the alclad but so what? Follow Van's sensible recommendations as found here and your RV will outlast you.Does scuffing the surface of alclad aluminum with red scoth-brite pad remove the alclad?
Do scratches in the alclad need to be buffed out?
The fact is, it takes very little scrubbing to remove the alclad. With a light scrubbing, especially with maroon scotchbrite, the surface will take on a satin look. This is a good thing because you want to rough the surface to promote good adhesion for the primer coat. Even a normally tenacious epoxy primer will flake off a pure alclad surface. As for fuel tanks, you must rough the faying surfaces (say bye bye alclad) so the proseal has something to grab onto.Okay, so to clarify what you guys are saying is that it takes a lot of scrubbing to totally remove the clad from the aluminum. My question then is ...is it necessary to totally remove the clad prior to priming, or do you only need to scuff the surface in order for the primer to adher to it?
The fact is, it takes very little scrubbing to remove the alclad. With a light scrubbing, especially with maroon scotchbrite, the surface will take on a satin look. This is a good thing because you want to rough the surface to promote good adhesion for the primer coat. Even a normally tenacious epoxy primer will flake off a pure alclad surface. As for fuel tanks, you must rough the faying surfaces (say bye bye alclad) so the proseal has something to grab onto.
Yes, using a Scotchbrite pad removes the Alclad, and you will need to prime the surface afterward to prevent future corrosion. If you plan on "buffing it out," as you put it, then you are basically referring to polishing the aluminum and having to maintain that polish throughout the life of the surface. Once the Alclad has been even minutely scratched---as with an Anodized or primered surface---the aluminum is vulnerable to the corrosion process. Hope this helps!
Stop sanding the pure aluminum anti-corrosive coating off of Alclad and just use the primer - it sticks to the pure aluminum surface without needing to scuff it up.
How much does it make to remove the best anti-corrosion coating the metal can have in order to apply an anti-corrosive coating?
I don't believe this to be accurate. I don't know the spec, but I suspect the alcad layer to be about 1 mil or more. Red scuff pads (approx 400 grit) will leave scratches that are well under .1 mil (400 grit has an Ra of .23 microns). I sanded my alclad sheets before priming with 120 grit sandpaper. I tested before hand to see if I would break through the alclad. I had to sand the **** out of the test panel to break through with the 120 grit on a DA sander. I removed about a mil (.001") before breaking through. Not something you could do with a red scuff pad without working at it pretty hard.
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Do your homework on understanding WHY alclad has a pure aluminum surface
Why is anyone removing the pure aluminum surface of Alclad whether by scuffing or any other means? Have people lost their minds? I know of A&P mechanics that apparently eeked their way through A&P school without reading and have continued throughout their life without reading. Had they been curiousness enough to ask "what is Alclad" and then ask why the alloy has a pure aluminum coating they would shine like a diamond amongst a bin full of lumps of coal. Never in my life would I ever imagine people could be so incompetent or ignorant as to remove the pure aluminum coating in order to apply a conversion coating or an aerospace epoxy primer. I've seen people try to alodine alclad and actually COMPLAIN that the surface didn't accept the alodine after the acid etching and soaking in alodine - so they remove the pure aluminum coating by sanding it off. How much does it make to remove the best anti-corrosion coating the metal can have in order to apply an anti-corrosive coating?
Stop sanding the pure aluminum anti-corrosive coating off of Alclad and just use the primer - it sticks to the pure aluminum surface without needing to scuff it up.
Stop the insanity
Not to mention Sonexes, Zeniths, the odd Thorp here and there, and who-knows-how-many others.Holy necro-thread Batman! You do realize this debate occurred 10 years ago, right? A whole bunch of RVs have been built in the interim without folks getting too spun up about this.
Not to mention Sonexes, Zeniths, the odd Thorp here and there, and who-knows-how-many others.