How is the corrosion resistance of PH stainless steel compared with martensitic stainless steel?

PH stainless steel contains higher chromium and nickel content than standard martensitic stainless steel such as 440C, forming a denser passive oxide film on its surface. It delivers much stronger resistance to atmospheric corrosion, freshwater, seawater splash and mild organic acid environments. Martensitic stainless steel easily generates rust spots under humid conditions, while properly aged PH steel maintains stable anti-rust ability without extra surface coating. It still cannot resist strong hydrochloric acid or concentrated chloride media, which limits its use in severe chemical reaction equipment.