A few months ago, while cleaning, I took the plastic cover off the back (of the inside) of my freezer (covers the fan and the cooler) and things looked fine:
I didn't put the cover back on and later noticed this metal thing went rusty:
(That's not really 'regular' iron rust, it's somehow soft and kind of greasy.
That is also the reason why the fan is unplugged in the second photo. It spatters crumbs/drops of this rust around when it's running.)
So I took the metal part off, cleaned it with bathroom cleaner and steel scourer/scrubber and put it back in. Some time later, it got rusty again. (I hadn't put the cover back)
So, what I would like to know is: does it go rusty because there is no cover?
Can I clean it again and put the cover back and rest assured it will not go rusty again underneath it?
Or do I have to replace it? What is this material anyway? Zinc? Does it have a special purpose apart from holding the fan and its motor in place?
Many thanks in advance!
Best Answer
From my point of view this metal part is a base plate which makes it possible to mount the fan onto the plastic parts.
As RedGrittyBrick noted, it is (or better was) zinc-plated. It seems to me, that most of the zinc layer is oxidized and cannot provide galvanic protection anymore. So why did it loose the zinc layer so quickly?
If it was behind a cover before, it might be, that the cover was to protect the fan and the base plate from humidity and corrosive vapours. Food can emit corrosive vapours like vinegar and almost certainly a lot of water even at temperatures below freezing point.
But the usage of bathroom cleaner might have been the death sentence for the zinc layer, because bathrom cleaners are highly acidic and can dissolve zinc quickly.
Anti rust primer can do the trick but you will have to coat the part carefully and without gaps. After that you can coat it with an additional protective layer. And you should try to get some stainless steel screws equivalent to those used there, as it is impossible to coat the screws.
There's one major drawback on using anti rust primer and other coatings inside your freezer. They tend to evaporate VOC and other nasty things in return which may enter your food. Something I wanted to avoid.
Alternatively you could clean the part thoroughly from any rust and screw some magnesium or zinc liner onto it. This liner will jump in for the lost zinc layer. And put the cover back on to reduce the amount of humidity reaching that part.