I'm dealing with some hydrocarbons (diesel, gas oil, kerosene, ethanol) where I'm putting them in a chamber and shining light through them to hit a sensor on the other side in order to measure their colour. Unfortunately what I'm finding is that the lenses and reflective surfaces in the chamber that I'm using for these optical measurements are being stained by the products and subsequently affecting the measurements. When the chamber is emptied, small amounts of product remain clinging to the internal surfaces. As this dries a residue is left which remains on the surface.
I've tried a couple of different materials: stainless steel reflectors, transparent Grilamid plastic lenses, a stain-resistant transparent potting and regular glass. All of them end up with a residue that clings to the surface that needs to be wiped clean. Unfortunately, for my application I'm not going to be able to get access to the internal surface to clean it so I need to find a way to prevent this residue from clinging to the internal surfaces.
The main restriction for me is that the system needs to basically be 100% maintenance free, and unfortunately I can't control the fluid coming in and out and therefore can't rinse the system out.
I was wondering if there are any products (both transparent and reflective) that are basically completely "hydrophobic" but for hydrocarbons and will prevent the product clinging at all to the surface and staining the lenses and reflectors?