Heater Issues (pics)

[StevieDS]

Has anyone else had this problem with heating elements? These pics were taken after soaking in baking soda, vinegar, citric acid, star san and a good scrub with a brillo pad, so the black areas are not burnt on crusty stuff, it's as if the metal has discoloured.
It's a 4kw element but it's about 300mm long so it's a fairly low watt density.
This was about the 5th time I've used this element, it was really well cleaned after each use.
I've had this problem in the past using asda and Tesco kettle elements, I went through 4 or 5 of them before deciding to get something "more sturdy". One of my brews actually ended up down the drain due to scorched wort.
So with this one, I have it running at about half power during the boil, controlled by a voltage regulator.
Also it was not a ridiculously long boil, only 75 mins.
It's really annoying, in the past each element has crapped out shortly after this staining happened.
Any ideas what's going on here?

 

[Fil]

looks like the acid solution has effected the metal, if its not flaking off i wouldnt worry too much unless the metal now starts to rust, a wipe with a dry tissue after leaving in the air overnight after a wetting will reveal red colour if its prone to rust.

i had ebay stanton elements which were plated and after a boil or 2 started to loose the plating, but a kitchen scrubby less abrasive than a brillo pad scraped the silver plating back to base brass.

 

[StevieDS]

So do you think, as long as its not flaking or rusting, it's just superficial?
I'm getting pretty fed up replacing elements

 

[Fil]

Im far from expert but if its just a tarnish due to exposure to an overly acid solution and heat, and shows no other signs of deterioration such as flaking, rusting or pitting, i would be content using it.

My experience is limited to elements that did loose platting revealing a yellow brass base, and as brass can leach out lead ?? i dropped those pdq. if yours remain inert i would think they will be fine.

After a single boil, small black flecks where the platting had fallen off

after attacking with the scrubby side of a kitchen sponge

I then went 100% SS brewing elements from the homebrewbuilder.co.uk