Inside compressor rusty

[Aria]

Hello all,

Happy wednesday,

I want to discuss about compressor. In field, some of compressor were locked. after breakdown, inside of compressor was rusty/corrosion. After discuss with compressor maker, their explanation almost same, rusty is cause by some air/moisture inside of compressor.
But, i already try inject some water (5 gr - 10 gr) to the compressor, and running on high ambient temperature (43 C). after 5-6 month, breakdown the compressor, there is no rusty inside and compressor still running well.
Is there any specific condition that can make inside compressor rusty ?? as we know the POE oil is higroscopic.

i also attach some of picture.