Spark emission spectroscopy analyzes surface contamination of metals. This technique controls the quality of surface preparations and is useful in fundamental investigations of surface properties of metals

Grove, E. L.

Losele, W. A.

English

NASA Technical Reports Server

June 1969	 Brief 69-10192 
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. 
Detecting Hydrogen-Containing Contaminants on Metal Surfaces 
22 . 
.
A spark emission spectroscopy technique has been 
developed for the analysis of surface contamination of 
metals. This technique can readily be applied in con-
trolling the quality of surface preparations in addition 
to being useful in fundamental investigations of surface 
properties of metals. 
The problem: 
Porosity is by far the most common type of defect 
found in aluminum alloy welds. Hydrogen has been 
positively identified as the direct cause of porosity. 
The differential solubility of hydrogen in molten and 
solid aluminum and the subsequent precipitation (in 
the form of hydrogen bubbles) upon solidification has 
been identified as the mechanism for this porosity 
formation. 
The solution: 
Since the preparation of "good" weld joints presup-
poses a surface relatively free of absorbed hydrogen-
bearing contaminants, a quantitative surface analysis 
is required to measure the contaminant concentration. 
It has been found that surface absorbants can be 
ionized by high-voltage sparks. A specially designed 
sparking chamber and support instrumentation for 
analyzing the emission structure of the ionization were 
assembled in order to utilize this technique. 
How it's done: 
A spark chamber has been constructed which makes 
it possible to measure background conditions and 
sample surface without disrupting the equilibrium of 
the system; the chamber consists of a brass base plate 
and cover, and a pyrex cylinder for the wall. A rotating 
stage carries the sample and the lower electrode, the 
upper electrode being supported by the top cover. A 
pair of standard electrodes is provided for internal 
calibration.
Carrier gas is injected through a diffusion plate into 
the chamber volume. Supporting hardware includes 
a LN 2 trap in the carrier gas line and controls for 
chamber pressure and gas flow rate. 
Standard operating procedure employed with the 
chamber consists of a twenty minute purge of the 
system with a 95% He-5% Ar mixture, a one minute 
preblank spark between the calibration electrodes, a 
five minute purge during which the sample specimen 
is positioned below the upper electrode, a one minute 
sparking of the specimen, another five minute gas 
purge and a final spark calibration. Spectrographic 
plates are exposed during each spark cycle and analysis 
of the recorded emission structure is performed by 
conventional densitometric procedures. 
Note: 
Further documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69- 10192 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: E. L. Grove, W. A. Losele

and Z. P. Saperstein of 
lIT Research Institute

under contract to

Marshall Space Flight Center

(M FS-20456) 
Category 03 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Detecting hydrogen-containing contaminants on metal surfaces

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