This study investigates corrosion of carbon steel balls and the valve seat during acid cleaning in inhibited HCL(1) solution. The ball and seat were electro less nickel plated followed by tungsten carbide and Inconel 625 via HVOF(2) technique respectively. Weight-loss testing showed that corrosion rate was 137.4 MPY(3) over an exposure period of 6 hours in 10 Vol % (Volumetric) inhibited HCl solutions at 35 °C for Inconel 625 coupons. The 32 inch valves were exposed to inhibited HCl solution with different concentrations (3 Vol%, 8 Vol%, 12 Vol% and 15 Vol% with maximum pH=2) accordingly. Exposure time varies from one to ninety hours. Due to poor sealing of some ball valves after chemical cleaning, corrosion resistance of eighteen coupons were evaluated by EIS(4) The coupons were coated under similar conditions to that of balls. In this case study, corrosion mechanism affecting the extent of damage on each coating along with surface properties and material is discussed.

Subject
Acids, Electrochemical impedance spectroscopy, Coatings, Materials, Substrates, Corrosion rate, Valves, Nickel based alloys, High velocity oxy fuel spraying, Tungsten carbide, Immersion, Corrosion resistance, Polarization resistance
Keywords:
Corrosion, Coating, Inhibited HCl, Tungsten carbide, Inconel, Polarization, Impedance
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2018
Association for Materials Protection and Performance (AMPP)
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