The article investigated the characteristic features of pitting of plate-like heat exchangers made of AISI 304 steel in model circulating waters. It was established that the critical pitting temperature (CPT) of AISI 304 steel increases with an increase in the pH of the model circulating water from 4 up to 7 and rapidly decreases at pH8. It was recorded that under such conditions the influence of the chloride concentration in them on the CPT of the studied steels is absent. It was found that regardless of the chloride concentration in the model circulating water, the CPT of AISI 304 and 08Kh18N10 steels rapidly decreases with an increase in the volume of δ-ferrite to 0.05 vol%, but then this process slows down at a volume of δ-ferrite from 0.05 up to 0.12 vol%. It was established that in weakly acidic model circulating waters with pH4 and a chloride concentration of 350; 600 mg/l CPT of AISI 304 steels decreases linearly with an increase in their specific paramagnetic susceptibility χ0 of austenite from 2.23 × 10–8 up to 2.31 × 10–8 m3/kg. It was found that the linear correlation coefficient between these values decreases from 0.73 in an media with a chloride concentration of 600 mg/l to 0.61 with 350 mg/l. This is due to a decrease in the contact area of the base metal of the steel in pittings with a chloride-containing medium, since the same trend was found in model circulating water with pH5 and the opposite in a highly oxidizing chloride-containing medium. When manufacturing heat exchangers from AISI 304 and 08Kh18N10 steels, it is recommended to choose melts with a specific paramagnetic susceptibility χ0 of austenite from 2.26 × 10–8 up to 2.31 × 10–8 m3/kg, a δ-ferrite content of up to 0.05 vol% and a minimum volume of oxides.