In plate heat exchangers, it is crucial to select appropriate plate materials based on the corrosiveness of the different heat exchange media involved.
904L, SUS890L Stainless Steel:
This is an austenitic stainless steel with a good balance of price and corrosion resistance. It is particularly suitable for acids such as sulfuric acid, phosphoric acid, and halides (including Cl-, F-). Due to its high content of Cr, Ni, and Mo, it exhibits excellent resistance to stress corrosion, pitting, and crevice corrosion. Suitable for use in chlorine-containing media.
254 SMO Advanced Stainless Steel:
An ultra-low carbon advanced stainless steel improved from type 316 by increasing the Mo content. It has excellent resistance to chloride pitting and crevice corrosion, suitable for media such as saline water and inorganic acids where type 316 is not applicable.
Titanium:
Non-alloyed titanium, lightweight with a density of 4.51, naturally forms a passive protective film (Ti2O3). It possesses superior corrosion resistance compared to stainless steel and is suitable for chloride-containing media (Cl- concentration > 200mg/L, temperature ≤ 130℃). It practically does not corrode in seawater below 120℃ and various concentrations of saltwater (NaCl) below 165℃.
anium also exhibits good corrosion resistance in organic acids (e.g., concentrated nitric acid, concentrated carbonic acid), and dilute alkaline solutions below the boiling point.
However, titanium’s resistance to corrosion is poor in H2SO4, HCl, HF, aqua regia, etc. It may also experience crevice corrosion or stress corrosion in certain concentrated chloride solutions (e.g., wastewater with pH > 7, chloride concentration > 200mg/L) above 120℃. In such cases, titanium-palladium alloy should be chosen.
Titanium-Palladium Alloy:
This is titanium with added palladium (0.12%-0.25%), significantly improving its corrosion resistance in acidic media, especially under less demanding conditions. It exhibits good corrosion resistance to concentrated nitric acid, hydrochloric acid containing oxidizing ions (such as Fe+, Cu+), plating solutions, etc. Additionally, it can be used in dilute sulfuric acid (concentration ≤ 10%, temperature ≤ 70℃).
Nickel 200:
A pure nickel plate containing over 99% nickel. Primarily used in highly concentrated (50%-70%) and high-temperature (up to boiling point) caustic alkali solutions (NaOH, KOH, etc.). However, it is sensitive to crevice corrosion caused by slightly salty water.
Hastelloy C-276:
Exhibits excellent corrosion resistance: almost unaffected by Cl-; excellent resistance to various concentrations of sulfuric acid, suitable for hot concentrated sulfuric acid; widely used in organic acids (such as formic acid, acetic acid), high-temperature HF acid, and certain concentrations of hydrochloric acid (< 40%), phosphoric acid (≤ 50%); chloride, fluoride, and organic solvents (such as methanol, ethanol).
Monel 400:
A nickel (about 70%) – copper (about 30%) nickel-based alloy. Exhibits good corrosion resistance in non-aerated sulfuric acid below 80% concentration and temperatures not exceeding 50℃~100℃, hydrofluoric acid below 50% concentration and temperatures below 100℃, acetic acid, and caustic alkalis. Particularly suitable for acidic chloride solutions and slightly salty and saline water under certain conditions; good high-temperature resistance. However, unsuitable for concentrated sulfuric acid, hydrochloric acid, and nitric acid, and very sensitive to mercury (sometimes present as impurities) corrosion.
Incoloy825:
Suitable for various concentrations of sulfuric acid at low temperatures; exhibits good corrosion resistance in caustic alkalis (such as NaOH) solutions of 50%-70% concentration without stress corrosion cracking. However, it is very sensitive to crevice corrosion caused by chlorides. Additionally, its stamping performance is not ideal, hence not commonly used as plate material.