A system for characterizing and optimizing refinery feedstock blends according to their corrosivity is provided. Refinery feedstocks can be characterized based on any of: dissociation of acids in the crude, breakup of naphthenic acid molecular associations, mass changes of carbon steel samples, and/or dissociation of sulfur compounds in the feedstocks. The characterization can be carried out via any of impedance, spectroscopic measurements, and continuous measurements of mass changes of carbon steel samples with a crystal microbalance over a range of temperature, e.g., from ambient to 750° F. The system can be employed in any of refinery, terminal, and laboratories, using models and/or hardware to optimize the usage of refinery feedstocks in the blending and valuation of the feedstocks.