Study resulting in a satisfactory stress corrosion cracking test with extremely consistent results produced six new analytical methods. Methods detect and determine differences in the minor constituent composition of different types of dinitrogen tetroxide

Clarke, J. F. G., Jr.

Conner, A. Z.

Gailey, J. A.

Orr, A. A.

English

NASA Technical Reports Server

July 1972	 B72-10321 
r NASA TECH BRIEF 
Marshall Space Flight Center 
NASA Tech Briefs announcenew technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Titanium Alloy Stress Corrosion Cracking
in Presence of Dinitrogen Tetroxide 
A report has been published which discusses inter-
actions between liquid dinitrogen tetroxide (N204) and 
6Al-4V-titanium alloy that lead to stress corrosion 
cracking. The study was almost exclusively focused on 
establishing the chemical composition of the minor 
constituents of reactive and nonreactive N 2 04 systems. 
As a result of this effort, a satisfactory stress corrosion 
cracking test was developed and found to give extremely 
consistent results. Six new analytical methods were 
developed that are capable of detecting and determining 
significant differences in the minor constituent compo-
sition of different types of N 2 04 . These include: 
(1) combined nitric oxide (visible spectrophoto-
meter); 
(2) total protons; 
(3) distribution of protonated species (near-infrared 
spectroscopy); 
(4) dissolved oxygen (gas chromatography); 
(5) combined chlorine (x-ray fluorescence); and 
(6) metallic impurities (atomic absorption). 
Methods (1) and (4) permit analyses to be made at 
previously unattainable low levels. Method (2) represents 
a major analytical breakthrough. It is now possible to 
establish the amount and nature of the protonated 
species in samples of liquid N 2 04 . Oxygenated N204 
was found to contain only HNO 3 ; nonoxygenated 
N2 04 was found to contain variable amounts of HNO3, 
HNO 2 , and H2 0. In addition, techniques were developed 
for the quantitative adjustment of the minor constituent 
composition of N 2 04 systems, including a method for 
substantially reducing the level of protonated species. 
By application of the above. techniques and methods, 
it was possible to prepare and test a wide variety of 
N2 04 compositions. As a result, the stress corrosion 
cracking (SCC) test behavior of 6A1-4V-titanium alloy 
in the commonly encountered types of commercial 
N2 04 was established. Correlation of combined NO-
protonated species concentrations with SCC test be-
havior was partially achieved in terms of critical con-
centrations. An interdependency between combined NO 
and protonated species concentrations was shown to 
relate to SCC test behavior. An attempt also was made 
to establish the effect of dissolved 0 2 concentration. 
It is now believed that the presence of HNO 2 and/or 
H2 O species in N 2 04 are the main critical indicators of a 
nonreactive system that is free of extraneous contamina-
tion. However, the nature of the inhibitory process has 
not been established. The available evidence appears to 
favor the hypothesis of an oxidative attack mechanism, 
although the specific nature of the attacking species 
remains unknown. 
Note: 
Additional information may be obtained from: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&TS-TU 
Huntsville, Alabama 35812 
Reference: B72-10321 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to: 
Patent Counsel 
Marshall Space Flight Center 
Code A&TS-PAT 
Huntsville, Alabama 35812 
Source-: A. Z. Conner, J. F. G. Clarke, Jr., 
J. A. Gailey, and A. A. Orr of
Hercules, Inc.
under contract to
Marshall Space Flight Center 
(MFS .21 113) 
Category 04 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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Titanium alloy stress corrosion cracking in presence of dinitrogen tetroxide

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