Black Anodising Discolouration

Thanks for that. I'm trying to remember the conditions these cameras are used in. There could be high UV, I'll find out tomorrow. The electrolytic colouring is something worth investigating.

Is the substrate leaching ? Not my field, but 20 years makes me wonder. I am, as usual, speculating out of my rear end. 'more than one plater' would also make me consider what might be going on.

We had a full batch of items fade to a dark gold or light brown. We had years of reports of rust stains all over the outside of our aluminum enclosures.

Items properly finished would stay black but fade a little from a jet black to a less pronounced black.

https://www.pfonline.com/articles/electrolytic-coloring-and-corrosion-resistance

Is this true of all cameras, or just the ones at this location? Are all of this customers cameras fading, or just in a specific area?

"White" L.E.D. lamps are also a great source of U.V. Many chemicals and elements will cause this

We had some black anodized equipment that was never exposed to the sun. There was one blue LED projecting through the aluminum. After a couple of years all the equipment had a very faded ring around the LED.

We've had this with other cameras previously but not to the extent of these.

It has often been said on Antiques Roadshow that removing the patina greatly devalues the, " object de art " .

I can try that argument, not sure it will wash.

Could it be the result of "energetic cleaning" with metho, isopropyl or simiar where the abrasive cloth has removed minute layers of the coating and now you are seeing the substrate filtered through an ever decreasing layer of coating. Essentially polished off like silver plating can be.

If the observation is NOT seen inside recessed screw holes and such, then this might be the cause.

From the picture provided, all areas that are purple are the easily "polished" places.

The field containing the Conformité Européene CE logo is a nice matte black. Why not use the same finish on the part tuning purple ?

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thewildotter

That's partly what makes this so difficult to understand. All of those parts were made by the same sub-contractor & would have been anodised at the same time by his plater. The only difference I can think of is that the part with the markings would have been from plate & the other parts from bar.

just review my site:

https://www.tksindustrial.com/voc-concentrator