Aluminium corrosion and other issues....

a_retent has provided the best answer so far. Unless ALL of the corrosion is removed, it will only bubble up again. Alodine treatment is really good but the chemicals are getting harder to find. If you have ever looked at aircraft parts and seen aluminum with a slight yellowish gold color, that's alodine. Most times it's painted over but a lot of times in electrical chassis it's left in it's natural state.
What I do on a lot of aluminum pieces that I restore is to first glass bead, clean with acetone and than give it a light coat of metal etching primer made for aluminum. Paint as desired.
A good turntable deserves a good restoration. They stopped making them.

BillWojo
 
Thanks for the US Navy opinion. It's a TT for indoor use... not a battleship or aircraft. This paint surface is blistered because of grease most likely, finger prints all over.. NZ New Zealand!

It's not about the Navy, that just happens to be where I received my education credentials to speak objectively on the subject. I'm well aware the object of this conversation is not a battleship or aircraft but what you need to understand is aluminum is aluminum no matter what form it's shaped into or what it's designated use may be, if left untreated or cared for it'll corrode into a pile of white powdery dust. Just so you know battleships are primarily made up of steel whereas aircraft, which are very expensive, whether they be military or civilian are made up of a lot of aluminum, which if your not able to figure out is what the turntable base here is made of. As for the fingerprints (corrosive contaminates) if left in place and never cleaned creates an electrolytic bridge between positive and negative charges in the material it's applied to which aids in the start of the corrosion breakdown process. The reason Navy aircraft get washed with fresh water often is saltwater spray dries and leaves the salt mineral (corrosive contaminates) which creates that electrolytic bridge that starts the material breakdown process. The reason Navy aircraft get inspected every 20 and 40 day intervals is to attempt to stay ahead of the corrosion process by eradicating the problem in its earliest stages so corroded panels don't fly off in flight causing the plane to fall out of the sky as they are expensive to replace.

Your fingerprints contain many things, acid, enzymes and so on, anyone of which can aid in the start of the corrosion process. That green slime you see in the pictures is a form of corrosion and more than likely the chemical reaction between the enzymes or acid in the fingerprints and the material it's sitting on. Ever placed a brass house key in your mouth for convenience while carrying an arm load of stuff through the door and then a short time later fire up a cigarette or had a beverage? That disgusting taste you experiece is the after effects of the chemical reaction between your saliva and the brass oxide left behind after you took the key out of your mouth. That chemical reaction is short lived but imagine that reaction happening 24x7 for years on the surface of an unprotected control knob, that's why manufacturers put protective coatings on those knobs. The TT of this subject suffers from the failure of the protective coating to do it's job and therefore contaminates aided the corrosion process to begin, hence the bubbling of the paint. The moral of this story is keep your equipment clean, not only to keep your mama happy, but it can keep this problem at bay, however if left dirty with contaminates you see the results. BTW "grease" like in automotive/petroleum is typically a protectant not a corrosive, greasy fingerprints is a popularly misused term.

Glass beading small areas of corrosion does not have to be an expensive endeavor. I personally use a badger air eraser ($30.00usd) and a small 5 gal. air compressor ($89.00) which I needed anyways for tires, nail gun, blowing off dusty circuit boards, chasing my dog around the shop, using it as an excuse as to why I can't hear the wife, etc. The badger air eraser looks just like an air brush but you fill the glass material cup with blasting media, in this case glass bead. You can find glass bead media just about anyplace they sell sand blasting material. Because the media is inconsistent in size I use a screened tea strainer to sift out the bigger beads that can clog the air eraser. Despite what the instructions say I typically blast at about 80-90 p.s.i. as I like to get the job done. I also blast outdoors wearing chemical safety googles, respirator and hooded sweatshirt because that stuff gets everywhere after it bounces off the object your blasting @ 90 p.s.i. I've used my air eraser on many different things not only to remove rust and corrosion but have also masked a decorative accent on a side window to a front door and glass beaded the pattern onto the window. One time I had a thermostat gasket blow on my small block Chev and antifreeze sprayed all over my aluminum Edelbrock torker intake staining it. Using the air eraser and glass bead media the staining easily came off and the resulting finish looked excellent. Sprayed the intake with imron poly and it outlasted the motor itself. Sand blasting is not exclusive to any one country and I'm sure it's done in New Zealand, which I'm well aware of its location and that the OP lists that as his location.

And last but not least; you're welcome for my service to the country in which you reside, in addition the protection of the rights and freedom you use on a daily basis...it was truely my honor!
 
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