I have used ones similar to these for bag sensing in an industrial dialysis mixer. They are used to detect bags being in position for automatic opening process. The environment is similar to what you mention as citric acid wash is being blended by the machine. Afraid I can’t help on the “being wet” issue. Our enviroment is humid, but not directly being saturated at all times.
https://www.grainger.com/product/35T429?ef_id=Cj0KCQiA8vSOBhCkARIsAGdp6RRpuUmtyagfwljFgPw5_uvIr8j804T5cboXBe2TwYZ7ZWt0y1_fTMYaAi4oEALw_wcB:G:s&s_kwcid=AL!2966!3!496359975037!!!g!469674884107!&gucid=N:N:PS:Paid:GGL:CSM-2293:99F1R6:20501231&gclid=Cj0KCQiA8vSOBhCkARIsAGdp6RRpuUmtyagfwljFgPw5_uvIr8j804T5cboXBe2TwYZ7ZWt0y1_fTMYaAi4oEALw_wcB&gclsrc=aw.ds