Hydrogen-stress cracking in high-strength steels is influenced by hydrogen content of the material and its hydrogen absorption tendency. Non-embrittling cleaning, pickling, and electroplating processes are being studied. Protection from this hydrogen embrittlement is important to the aerospace and aircraft industries

Elsea, S. T.

Fletcher, E. E.

Groeneveld, T. P.

English

NASA Technical Reports Server

May 1967	 Brief 67-10141 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Study to Minimize Hydrogen Embrittlement of Ultrahigh-Strength Steels 
Atomic hydrogen is capable of entering steel and. 
many other metals and alloys; when it does, any of 
several undesirable phenomena can occur. If large 
quantities of hydrogen are introduced, there may be a 
general loss in ductility or, if the hydrogen accumu-
lates in certain localized areas, internal bursts or 
blisters may be produced. At elevated temperatures, 
hydrogen may react with and remove so much carbon 
from the steel that the material is no longer capable of 
supporting the design stresses. Under certain circum-
tances, hydrogen introduced into steel during its 
manufacture, subsequent fabrication, or in service 
may result in brittle failures at applied stresses far 
below the yield strength or the nominal design stress 
for the alloy. All of these phenomena are collectively 
referred to as hydrogen embrittlement. However, only 
the last, i.e., the catastrophic, hydrogen-induced, 
brittle failure of ultrahigh-strength structural steels at 
relatively low applied stresses is of interest in the 
present study. Since this phenomenon frequently 
occurs in materials that exhibit no appreciable loss in 
ductility (as measured by a conventional tensile test), 
it is often termed hydrogen-induced, delayed brittle 
failure, or hydrogen-stress cracking. 
Several conditions must be satisfied for hydrogen-
stress cracking of steels to occur: 
(I) The steel must be processed to a strength level 
above some as yet not clearly defined minimum; 
generally, as the strength level of the steel is 
increased above this minimum, the time for 
failure decreases. 
(2) The steel must be subjected to an applied tensile 
stress above some minimum value that is de-
pendent on the strength level of the steel; as 
the strength level of the steel increases, the 
minimum applied stress that will result in 
hydrogen-stress cracking decreases.
(3) The steel must contain hydrogen in excess of 
some minimum amount, and this hydrogen 
must be free to diffuse through the steel. 
In view of these conditions, it would be expected 
that any condition that alters the strength, applied 
stress, or hydrogen content of a given material could 
influence its sensitivity to hydrogen-stress cracking. 
The trend toward higher tensile strengths, higher 
design stresses, and the use of materials in applications 
requiring prolonged exposure to high sustained loads 
insures that two of the conditions necessary for the 
occurrence of hydrogen-stress cracking will be present 
in steel parts intended for certain aerospace and air-
craft applications. All that remains is for an adequate 
supply of hydrogen to be available and for this hydro-
gen to be free to diffuse through the steel. Thus, it 
appears that, for high-strength steels sensitive to 
hydrogen-stress cracking, the most important factors 
tending to promote hydrogen-stress cracking under 
these conditions are the hydrogen content of the 
material and the propensity of the material to absorb 
hydrogen from its environment, either during process-
ing or in service. 
The problem of hydrogen-stress cracking of ultra-
high-strength steels has become quite serious in the 
aerospace and aircraft industries because many of the 
components fabricated from these high-strength steels 
have to be protected from corrosion in their service 
environments. The preferred method of providing this 
protection is cadmium electroplating. However, the 
application of electrodeposited coatings to solve cor-
rosion problems can make the part susceptible to 
failure by hydrogen-stress cracking because, fre-
quently hydrogen is introduced during the cleaning 
and electroplating operation. 
Earlier studies showed that most ultrahigh-strength 
steels were embrittled to various degrees by virtually 
(continued overleaf) 
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all of the common electroplating processes, including 
cadmium, chromium, zinc, tin, nickel, lead, copper, 
and silver. These studies also showed that the amount 
of hydrogen entering steel specimens during certain 
electroplating processes may be as great as that 
introduced during severe cathodic charging, and that 
more hydrogen sometimes was introduced during 
pickling or cathodic cleaning prior to electroplating 
than during the actual plating operation. In addition, 
these studies showed that the sustained-load tensile 
test employing notched bars was the most sensitive 
method for evaluating the embrittling tendencies of 
cleaning and electroplating processes. 
The results of a literature and industrial survey of 
reportedly low-hydrogen-embrittling and nonhydro-
gen-embrittling cleaning, pickling, and electroplating 
processes (including cadmium, chromium, and nickel 
electroplating) and of various hydrogen-embrittlement 
relief treatments are described in: "A Review of the
Literature on Cleaning, Pickling, and Electroplating 
Processes and Relief Treatments To Minimize Hydro-
gen Embrittlement of Ultrahigh-Strength Steels," by 
T. P. Groeneveld, E. E. Fletcher, and A. R. Elsea, 
October 15, 1965, Batelle Memorial Institute. 
Note: 
Copies of the special report are available from: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B67-10141 
Patent status: 
No patent action is contemplated by NASA. 
Source: T. P. Groeneveld, E. E. Fletcher, 
and A. R. Elsea 
of Batelle Memorial Institute 
under contract to 
Marshall Space Flight Center 
(M-FS-2455) 
Brief 67-10141	 Category 03


Study to minimize hydrogen embrittlement of ultrahigh-strength steels

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