Water droplet impingement corrosion

In wet scrubbing the dust is removed by counter-current washing with a liquid, usually water, and the solids are removed as a slurry. The principal mechanism involved is the impact (impingement) of the dust particles and the water droplets. Particle sizes down to 0.5 /i.m can be removed in suitably designed scrubbers. In addition to removing solids, wet scrubbers can be used to simultaneously cool the gas and neutralise any corrosive constituents. 

Attack is further aggravated at higher temperatures and with solutions containing solids in suspension. Steam carrying water condensate droplets provides an aggressive medium for corrosion of sfeel and cast iron piping. The impingement of water droplets at the return bends destroys the protective oxide film and accelerates the attack on the substrate. 

Several environmental modifications can be implemented to minimize the risk of erosion corrosion. Abrasive particles in fluids can be removed by filtration or settling, and water traps can be used in steam and compressed air systems to decrease the risk of impingement by droplets. Deaeration and corrosion inhibitors are additional measures that can be taken. Cathodic protection and the application of protective coatings may also reduce the rate of attack. 

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