Application of insulated protective coatings for reduction of corrosion potential of type 304 stainless steel in high-temperature water

An approach was developed for achieving a low electrochemical corrosion pot ential (ECP) on structural materials exposed to high-temperature water, eve n without the addition or presence of reducing species such as hydrogen (H- 2). This approach uses highly insulating coatings (e.g., yttria-stabilized zirconia [YSZ]) on structural materials to restrict the oxygen (O-2) transp ort rate to the metal surface while simultaneously preventing formation of a differential aeration crevice cell because of its highly insulating chara cter. Initial experimental data on type 304 stainless steel (SS [UNS 30400] ) coated by air plasma spray showed ECP of YSZ-coated type 304 SS remained at approximate to -0.5 V-SHE in 288 degrees C water containing up to 200 pp b O-2 and no H-2.