I am in the process of building a fermentation temperature controller (in the same spirit as the grainfather glycol chiller), the process is mostly done and I am testing the system with water.
The heat exchange is made through a hand-bent copper tubing plunged in the fermentation vessel; the problem is, after a day or two, the water inside the vessel takes a light yellow tint and there is a rust spot at the bottom of the vessel (the chiller touches it).
So my questions are, will this affect the beer? Is there a way to prevent it? I am thinking the yeast will eat the oxygen, preventing oxidation but will it be enough? worst case scenario I'll buy an inox chiller but its a bit against the DIY spirit :)
Thank you for your time!