HydroFluoric acid

Hydrofluoric acid (HF) is very corrosive and can react with many metals, including cast iron, to generate hydrogen gas. Common stainless steel types, like 304 and 316, are not resistant to HF at any concentration or temperature. Higher grades of stainless steel may have some resistance, but they can still be attacked locally.

Corrosion rates in Hydroflouric Acid (HF)

Alloy	Notes	Concentration, %	Temperature		Time	Corrosion Rate		Ref
			C	F		mm/yr	mils/yr
316	—	3	21	70	—	1.25	49.1	1
316	—	5	21	70	—	2.33	91.8	1
316	—	5	40	104	—	7.8	306	1
316	—	1	50	122	—	1.82	71.8	1
316	—	2	50	122	—	5.3	209	1
316	—	5	50	122	—	15.9	626	1

904L	—	3	21	70	—	0.125	4.9	1
904L	—	5	21	70	—	0.18	7.2	1
904L	—	5	40	104	—	0.73	28.8	1
904L	—	1	50	122	—	0.23	9.2	1
904L	—	2	50	122	—	0.71	28	1
904L	—	3	50	122	—	0.85	33.5	1
904L	—	4	50	122	—	1.36	53/5	1
904L	—	5	50	122	—	1.82	71.6	1
904L	—	1	70	158	—	0.99	39	1
904L	—	2	70	158	—	2.0	80.2	1
904L	—	3	70	158	—	3.31	130	1

AL-6XN	—	3	21	70	—	0.08	3.2	1
AL-6XN	—	5	21	70	—	0.20	8.0	1
AL-6XN	—	5	40	104	—	0.82	32.4	1
AL-6XN	—	1	50	122	—	0.10	4.1	1
AL-6XN	—	2	50	122	—	0.43	16.9	1
AL-6XN	—	3	50	122	—	0.98	38.4	1
AL-6XN	—	4	50	122	—	1.42	55.9	1
AL-6XN	—	5	50	122	—	2.0	78.7	1
AL-6XN	—	1	70	158	—	0.54	21.1	1
AL-6XN	—	2	70	158	—	1.98	78	1
AL-6XN	—	3	70	158	—	3.05	120	1

C-276	—	2	70	158	—	0.23	9	7
C-276	—	5	70	158	—	0.25	10	7

C-22	—	2	70	158	—	0.23	9	7
C-22	—	5	70	158	—	0.36	14	7

625	—	2	70	158	—	0.51	20	7
625	—	5	70	158	—	0.41	16	7

400	saturated with air	25	30	86	24hr	1	37	17
400	saturated with air	25	80	176	24hr	0.28	11	17
400	saturated with air	50	30	86	24hr	0.2	8	17
400	saturated with air	50	80	175	24hr	1	39	17
400	purged with nitrogen	25	30	86	48hr	0.005	0.2	17
400	purged with nitrogen	25	80	176	48hr	0.061	2.4	17
400	purged with nitrogen	50	30	86	48hr	<0.003	<0.1	17
400	purged with nitrogen	50	80	176	48hr	0.01	0.5	17