Methods and apparatus relate to measuring corrosion rate. Flowing corrosive fluid contacts a metal coupon or object and results in an effluent stream. The effluent stream contains metal from the object due to reaction of constituents in the fluid with the metal. Analysis of the effluent stream measures concentration of the metal therein. Since the concentration of the metal in the effluent stream is indicative of mass loss from the object, calculations provide the corrosion rate utilizing weight of the metal that is eluted, surface area of the object and exposure time of the object with the corrosive fluid.