Q: Are the nickel-copper
alloys (such as UNS N04400)
acceptable for use in
accordance with the NACE
sour service standards?
A: This question has been asked frequently, usually in relation to a valve for
an upstream hydrocarbon application
involving sour water that also contains
chlorides. Nickel-copper alloys can be
an economical option for such applications. However, changes in the NACE
standards within the last decade have
complicated the issue.
The original version of NACE
MR0175 released in 1975 allowed
N04400 material with a 35 HRC maxi-
mum hardness requirement. In 1982,
N04405, the higher-sulfur, free-machin-
ing version of N04400, was balloted,
approved and added by addendum.
M35-1 and M35-2, two cast “equiva-
lents” of N04400, were balloted and
added to a 1991 revision.
Because NACE defines valve shafts
and stems as pressure-containing components, this material could no longer
be used for shafts and stems when
compliance with MR0175 was
required.
Shortly after NACE MR0175-2003
was released, it was converted to ISO
15156, which NACE then adopted
back as NACE MR0175/ISO 15156.
No changes were made regarding the
Material
N04400
N04405
M35-1
M35-2
M30C
N05500 Solution
Annealed, Solution
Annealed and
Age-Hardened, or
Hot-Worked and
Age-Hardened
NACE
MR0175-
2002
Yes
Yes
Yes
Yes
No
Yes
Table 1. Acceptable for Valve Components?
NACE
MR0175-
2003
NACE MR0175/
ISO 15156
1st Edition
NACE MR0175/
ISO 15156
2nd Edition
No No Yes
No No Yes
No No No
No No No
No No No
Wellhead and
Christmas tree
components (other
than bodies and
bonnets) and
internal, non-
pressure-retaining
valve, pressure
regulator and level
controller
components
Wellhead and
Christmas tree
components (other
than bodies and
bonnets) and
internal, non-
pressure-retaining
valve, pressure
regulator and level
controller
components
Wellhead and
Christmas tree
components (other
than bodies and
bonnets) and
internal, non-
pressure-retaining
valve, pressure
regulator and level
controller
components
NACE
MR0103
Yes
Yes
Yes
Yes
Yes
Yes
