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Metal discolouration due to (presumably) contact with fingers

Avon

Avon

pfm Member
I have an arm-board that looks the same as the one in the following picture, though I don’t know if it’s the same model. Around the mounting bolts etc. where I’ve touched it, the metal has turned grey. Only the ring at the top is affected. I haven’t tried using metal polish, but I wonder if this would be effective. I also don’t know if it’s plated or not, which might rub off if I use wire wool or cutting compound, though there's no sign of it flaking off. I’m wondering what might be the best way to go about this, or should I just leave it be? I’d have to buy some Brasso etc. before I could try it myself, hence the question.
new-at-armbase.jpg
 
That's a piece of stainless steel, it will polish out. There is no anodising on there, iron won't anodise like ally will. I can't see any plating there. However it can be cleaned up with wire wool, Brasso, or similar. Black stains will be iron oxides formed by the salts in your sweat and oxygen in the air. One tip - DO NOT clean steel with green nylon pads, they are hard and will leave scratches. Steel wool (wire wool) will not. I know, it makes no sense but it's true. Get 0 or 00 grade. You can slow down the rate of tarnishing (oxide formation) with normal furniture polish, car wax polish, a thin smear of Vaseline, etc. All will keep the oxygen off, to a degree.
 
Tricky to be certain, but the NAS finish on their aluminium components (which is what is pictured) is a very traditional one. Choose a cork, put it on some kind of spindle, glue a piece of emery to the bottom of the cork. Mount that in a drill press and work your way across the aluminium surface - each touch with the cork/emery produces a swirl pattern.
There is no bare SS in NAS TT hardware that I know of, and probably not on their tonearms either, but the latter I am open to be corrected on. If there is any SS, it is chemically blacked.

I would degrease with something like IPA, and then some distilled water and leave well alone.

The ones here show no abnormal discolouration.
 
Thanks both. It definitely isn’t stainless steel though, as it’s too light and it has a “less solid” sound when tapped with a piece of metal. It feels more like aluminium or else some non-magnetic alloy to me. Although the chamfers are shiny like steel, the rest is brushed like aluminium. But presumably you wouldn’t anodise something that’d been brushed with swirls? IPA had no effect and I did read somewhere that weeing on it would remove the discolouration (unknown).

I may have a go at polishing or cutting a hidden bit first. However, assuming it is made by NAS themselves, then I might try getting a second opinion from Penny first. I always seem to have problems that no one else has.
 
In effect, aluminium is always anodised, sort of.
Aluminium is fantastically reactive so that any exposed bare, pure aluminium, pretty much instantly gets an oxide layer (known as a passive layer).
Conventional anodising just uses electricity to put an extra thick layer of oxide on.

Here, the chamfers are probably formed in one go from a lathe tool, not turned, and the circumferential sufaces are just (moderately) fine machined finish.

The marks that worry you are near certainly normal and just part of perfectly normal ageing/darkening of aluminium.
 
stevec67 said:
That's a piece of stainless steel, it will polish out. There is no anodising on there, iron won't anodise like ally will. I can't see any plating there. However it can be cleaned up with wire wool, Brasso, or similar. Black stains will be iron oxides formed by the salts in your sweat and oxygen in the air. One tip - DO NOT clean steel with green nylon pads, they are hard and will leave scratches. Steel wool (wire wool) will not. I know, it makes no sense but it's true. Get 0 or 00 grade. You can slow down the rate of tarnishing (oxide formation) with normal furniture polish, car wax polish, a thin smear of Vaseline, etc. All will keep the oxygen off, to a degree.
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OT sorry..

But for me that's a really informative post, I've learnt something there about why I get black streaks on the valve runners on Radfords when I polish them, or at least try to revive and type of finish on nearly 60 year one steel.

The runners certainly have some blemishes, I'm not sure if they could be polished out. I've used brasso and elbow grease so far. I might try a little, fine wire wool.

Thank you
 
The non-woven pads, of the right grade, are very commonly used for finishing (polishing) plenty of metals, and paint, amongt other things. Just pick the right ones - the colour tells the grade but you will struggle to find a source to tell you what colour is equivalent to what grit of traditional abrasive.
 
I thought it looked like stainless, but it's a small screen to look at, so I'm probably mistaken. If it's ally, mild acids will remove tarnish. Maybe even those in pee. Certainly stuff like vinegar, wine, coca cola, lemonade etc. Test on a small area first, etc.
 
Vinny said:
The non-woven pads, of the right grade, are very commonly used for finishing (polishing) plenty of metals, and paint, amongt other things. Just pick the right ones - the colour tells the grade but you will struggle to find a source to tell you what colour is equivalent to what grit of traditional abrasive.
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It does just feel counter intuitive to polish something with a close relation to my metal pan scrubber. :)

I shall look for some fine grade, 00 I suppose.

Ta
 
chiily said:
I shall look for some fine grade, 00 I suppose.
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Probably better with 000. In terms of polishing to a high finish, 00 is still quite coarse. (000 is as fine as it comes, although you can find steel, s/steel and brass wire wools.)

ALL polishing media are abrasives, it is just a question of how fine - at some stage the scratches aren't visible
 
Agent Avon here, reporting back to PFM HQ. Since I know that soaking in vinegar is a recommended way of removing rust from iron, I decided to leave the top part in some Sarson’s for 24 hours. The black marks are now gone and so mission accomplished. The metal has maybe gone a bit darker in colour though, with a slightly mottled appearance, but it still shines and it looks just fine.
 
PS. The oxidation was mainly around the four steel bolts. The TT had been kept in a cellar for a year. I may see if I can find some stainless steel bolts to replace them.
 
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