Can Inconel 625 resist corrosion by strong acids such as hydrochloric acid (HCl) and sulfuric acid (H₂SO₄)?
1.Hydrochloric acid (HCl)
, and Inconel 625 will corrode significantly in all but very dilute, low-temperature HCl.
concentrations > ~5–10% HCl typically cause rapid general corrosion and potential pitting.
As temperature increases, corrosion rates rise sharply.
Aerated (oxygen-containing) HCl may show slightly better resistance than deaerated HCl, but this is often insufficient for practical service.
Inconel 625 is for continuous exposure to HCl unless the conditions are very mild (e.g., trace amounts, low temperature, well-aerated, and with strict control of contaminants).
2.Sulfuric acid (H₂SO₄)
H₂SO₄ behavior is strongly dependent on concentration and temperature.
Inconel 625 can show (e.g., very dilute acid or highly concentrated "oleum"/near-anhydrous conditions) where the environment is less aggressively reducing and passivation is possible.
mid-concentration range (roughly 10–70% H₂SO₄)-which is common in many industrial processes-H₂SO₄ is strongly reducing, and Inconel 625 will suffer .
Higher temperatures further accelerate attack.
Therefore, Inconel 625 is ; alloys with higher Mo and Cu (e.g., Hastelloy C-series, Alloy 20, or certain stainless steels in specific ranges) are often preferred, depending on concentration and temperature.
: Inconel 625 is (except very dilute, low-temperature, well-controlled cases).
: Inconel 625 is in the commonly encountered mid-concentration range; resistance is only possible in very dilute or very concentrated conditions.
(mm/year or mpy) for the specific concentration, temperature, aeration, and impurity levels (e.g., chlorides, oxidizing species).
