Media	Concentration, Percent by Weight	Test Temperature		Average Corrosion Rate Per year, Mils*
Media	Concentration, Percent by Weight	°F	(°C)	625 alloy	C-22 alloy	C-276 alloy	G-30 alloy

Acetic Acid	99	Boiling		<1	Nil	<1	1

Ferric Chloride	10	Boiling		7325	1	2	-

Formic Acid	88	Boiling		9	<1	1	2

Hydrochloric Acid	1	Boiling		1	3	13	1

	1.5	Boiling		353	14	32	-

	2	194	(90)	Nil	Nil	1	-

	2	Boiling		557	61	51	-

	2.5	194	(90)	72	<1	12	-

	2.5	Boiling		605	141	85	-

	10	Boiling		642	400	288	2364

Hydrochloric Acid + 42g/l Fe₂(SO₄)₃	1	200	(93)	238	2	41	803
Hydrochloric Acid + 42g/l Fe₂(SO₄)₃
	5	150	(66)	2	2	5	557

Hydrochloric Acid + 2% HF	5	158	(70)	123	59	26	97

Hydrofluoric Acid	2	158	(70)	20	9	9	10

	5	158	(70)	16	14	10	11

P₂O₅ (Commercial Grade)	39	185	(85)	1	2	9	-

	44	240	(116)	23	21	100	-

	52	240	(116)	12	11	33	-

P₂O₅ + 2000 ppm Cl	38	185	(85)	2	1	12	-

P₂O₅ + 0.5% HF	38	185	(85)	9	7	45	-

Nitric Acid	10	Boiling		<1	<1	7	<1

	65	Boiling		21	134	888	5

Nitric Acid + 6% HF	5	140	(60)	73	67	207	-

Nitric Acid + 25% H₂SO₄ + 4% NaCl	5	Boiling		713	12	64	-

Nitric Acid + 1% HCl	5	Boiling		1	<1	8	-

Nitric Acid + 2.5% HCl	5	Boiling		<1	2	21	-

Nitric Acid + 15.8% HCl	8.8	126	(52)	>10,000	4	33	14

Sulfuric Acid	10	Boiling		37	12	19	31

	20	150	(66)	<1	<1	<1	-

	20	174	(79)	<1	1	3	<1

	20	Boiling		91	33	39	54

	30	150	(66)	<1	<1	1	<1

	30	174	(79)	<1	3	4	<1

	30	Boiling		227	64	55	60

	40	100	(38)	<1	<1	<1	<1

	40	150	(66)	1	<1	1	<1

	40	174	(79)	35	9	10	2

	50	100	(38)	1	<1	Nil	<1

	50	150	(66)	25	1	4	<1

	50	174	(79)	58	16	12	10

	60	100	(38)	<1	<1	<1	<1

	70	100	(38)	<1	Nil	Nil	<1

	80	100	(38)	<1	Nil	<1	-

Sulfuric Acid + 0.1% HCl	5	Boiling		151	26	33	-

Sulfuric Acid + 0.5% HCl	5	Boiling		434	61	49	-

Sulfuric Acid +1% HCl	10	158	(70)	121	<1	11	-

	10	194	(90)	326	94	45	-

	10	Boiling		869	225	116	-

Sulfuric Acid + 2% HF	10	Boiling		55	29	22	53

Sulfuric Acid + 200 ppm Cl^-	25	158	(70)	110	11	12	-
Sulfuric Acid + 200 ppm Cl^-
	25	Boiling		325	215	186	101

Sulfuric Acid + 1.2% HCl + 1% FeCl₃ + 1% CuCl₂	11	Boiling		1815	3	42	1227

Sulfuric Acid + 1.2% HCl + 1% FeCl₃ + 1% CuCl₂ (ASTM G28B)	23	Boiling		2721	8	55	-

Sulfuric Acid + 42 g/l Fe₂(SO₄)₃ (ASTM G28B)	50	Boiling		23	40	250	7

* To convert mils per year (mpy) to mm per year, divide by 40.

Immersion Critical Pitting and Crevice-Corrosion Temperature in Oxidizing NaCl-HCl

The chemical composition of the solution used in this test is as follows: 4% NaCl + 0.1% Fe₂(SO₄)₃ + 0.01 M HCl. This solution contains 24,300 ppm chlorides and is acidic (pH2).

In both pitting and crevice-corrosion testing the solution temperature was varied in 5°C (9°F) increments to determine the lowest temperature at which pitting corrosion initiated (observed by examination at a magnification of 40X of duplicate samples) after a 24-hour exposure period (Critical Pitting Temperature), and the lowest temperature at which crevice-corrosion initiated in a 100-hour exposure period (Critical Crevice-Corrosion Temperature).

	Critical Pitting Temperature		Critical Crevice-Corrosion Temperature
Material	°F	°C	°F	°C

HASTELLOY^® C-22^® alloy	>302	>150	212	102
HASTELLOY C-276 alloy	302	150	176	80
HAYNES^® 625 alloy	194	90	122	50
HASTELLOY G-30^® alloy	158	70	104	40
FERRALIUM^® 255 alloy	122	50	95	35
Alloy 904L	113	45	68	20
Type 317LM Stainless Steel	95	35	59	15
Type 317L Stainless Steel	77	25	50	10
Alloy 825	77	25	≤23	≤-5
20CB-3^® alloy	68	25	≤23	≤-5
Type 316 Stainless Steel	68	20	≤23	≤-5

Critical Pitting Temperatures in Oxidizing H₂SO₄-HCl Solution

The chemical composition of the solution used in this test is as follows: 11.5% H₂SO₄ + 1.2% HCl + 1% FeCl₃ + 1% CuCl₂. This test environment is a severely oxidizing acid solution which is used to evaluate the resistance of alloys to localized corrosion. It is considerably more aggresive than the oxidizing NaCl-HCl test. Experiments were performed in increments of solution temperature of 5°C (9°F) for a 24-hour exposure period to determine the critical pitting temperature (the lowest temperature at which pitting corrosion initiated observed at a magnification of 40X of duplicate samples).

	Critical Pitting Temperature
Material	°F	°C

HASTELLOY^® C-22^® alloy	248	120
HASTELLOY^® C-276 alloy	230	110
HASTELLOY^® C-4 alloy	194	90
HAYNES^® 625 alloy	167	75

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HAYNES® 625 alloy Information

A Ni-Cr-Mo-Cb alloy with excellent strength to 1500°F (816°C), good oxidation resistance, and good resistance to aqueous corrosion.

HAYNES^® 625alloy Information