[shvcko99]

In most cases I find that the term "leach" is used with food, e.g. leach into food.

What does the term "leach" actually mean? Could something leach into non-food? Is it the same as evaporation or sublimation?

What is the condition that would favor the process of "leach"?

[Hunter2]

Leach means to clean a container, machinery, and others by using a chemical like a  base, acid, bleach, etc.
And it means to remove something from another material.

[Corribus]

In the context the thread opener uses it, leaching means the diffusion/transfer of some substance contained within one phase (area/region) to another phase (area/region). For instance, if a lead pipe is placed in the environment, lead atoms may leach (transfer) from the pipe into the environment. Frequently this occurs because of a concentration differential between the two environments - substances tend to go from regions of high concentration to those of low concentration. It may be strictly a surface phenomenon or diffusion from the interior of a solid, as frequently occurs with substances contained in polymers.