Table 3 Potential materials of construction for mills to grind dilute acid-pretreated samples. Corrosion rate tests were performed at the sulfuric acid boiling temperature [47]

Irons and steels

 Altemp A-286

Solution treated

10

NR^a

0.75

 Stainless steels

  AL 29-4-2

Dilute^b

10

NR

0.46

  Altemp 625

Dilute^b

10

NR

0.64

  E-Brite

Dilute, nonactivated

5

0.356

  Type 316 stainless steel

NR

0.25

0.0686

 Titanium

  Ti-3-8-6-4-4

Plus 1 g/L FeCl₃

10

NR

0.15

  Ti-3A1-2.5 V

ASTM grade 9

0.5

NR

0.35

  Titanium

Grade 7 plus 16 g/L Fe₂(CO₄)₃

10

NR

0.178

  Titanium

Grade 12. naturally aerated

1

NR

0.91

 Tantalum

  Tantalum

NR

10

NR

<0.02

 Alloys

  Alloy C-22

NR

20

NR

0.838

  Alloy C-4

NR

10

NR

0.787

 Alloys

  Ferralium

NR

5

NR

0.30

  Hastelloy B

SO₂ purge

10

NR

0.05–0.25

  Hastelloy B-2

SO₂ purge

10

NR

0.05–0.25

  Hastelloy C

Lab test

10

>0.25–0.51

  Hastelloy G

Lab test

10

>0.25–0.51

  Hastelloy G-3

Lab test

10

>0.25–0.51

  Hastelloy G-30

Plus 42 g/L Fe₂(SO₄)₃

50

NR

0.171

  Hastelloy G-30

Plus 10 % nitric acid

50

NR

0.406

  Inconel 617

Average of two tests

5

NR

0.61

 Others

  Columbium^c

10

NR

<0.12

  Niobium

NR

10

NR

0.125