Quick question.

There are a number of threads, blogs and vlogs that talk about the inadvisability of using a pen with metal parts in the barrel as an eyedropper. Does anyone know for sure whether, for example, a pen with metal section threads will actually corrode if used this way.

I ask because most of the stuff I've read/seen seems like 'received wisdom' rather than actual experience, and bearing in mind the plethora of non-corroding (within our lifetime) steel nibs that have constant contact with ink.

Further to this, in the spirit of ongoing inquiry, what exactly are metal section threads or metal cartridge holders made of that leads to this supposed corrosion?