Engineering Bulletin

Corrosion of Common Alloys in Dry Chlorine (Cl2)

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In a couple of previous issues of our Engineering Bulletins we have already shown how Chloride / Chlorine levels in aqueous environments would affect alloy selection, and how calculation of PREN (Pitting Resistance Equivalent Number) would help in selection of an appropriate alloy for pitting corrosion resistance.

This short Bulletin considers corrosion of common alloys by dry chlorine. Well, dry Chlorine (Cl2) is not corrosive to steels at ambient temperatures and is commonly shipped and handled in carbon steel equipment, with higher-alloy materials such as Monel 400 and Hastelloy C-276 used for critical parts. The main factor that influences corrosion rates of steels by dry chlorine is temperature. Stainless Steel alloys can be usable up to about 300°C (570°F).

Corrosion rates of different alloys in dry chlorine and temperature (°C) at which given rates are exceeded are presented in the table below. Keep in mind that moisture will greatly accelerate attack of any of these materials with the additional danger of SCC (Stress Corrosion Cracking) of stainless steel.

Corrosion of some common alloys in dry Chlorine (Cl2)

Penetration Rates, [inches/year] and °C at which Given Rate is Exceeded.
Alloy 0.005″ 0.01″ 0.05″ 0.10″ 0.50″
Inconel 600 489 504 540 556 596
Inconel 625 484 500 534 545 589
Hastelloy C-276 473 488 522 538 579
Inconel 825 388 407 451 472 527
ss Alloy 310 362 383 434 465 536
ss Alloy 316 339 358 407 431 492
ss Alloy 309 354 390 406 448
ss Alloy 304 341 375 393 434
ss Alloy 321 341 375 393 434

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Disclaimer: The info presented here has been compiled from sources believed to be reliable. No guarantee is implied or expressly stated here and the data given is intended as a guide only.

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