Corrosion of 1100 aluminum in oxygen-saturated water at 70 degrees C under experimental conditions was studied, emphasizing effects of exposure interruption, the number of specimens, and the refreshment rate. A logarithmic equation was derived to express the corrosion rate

Draley, J. E.

Loess, R. E.

Mori, S.

English

NASA Technical Reports Server

December 1967
	
Brief 67-10578 
AEC-NASA TECH BRIEF 
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Study of Corrosion of 1100 Aluminum 
A study was initiated to determine the corrosion of 
1100 aluminum in oxygen-saturated water at 70°C 
under varioui experimental conditions. The effects of 
exposure interruption, the number of specimens, and 
the refreshment rate were studied. 
The water used for the corrosion tests was of high 
purity (less than 50 ppb impurities). Oxygen was 
bubbled through it until it was saturated. Up to eight 
extruded 1100 aluminum rods were suspended on 
Pyrex glass hangers and immersed in the oxygen-
saturated water. The temperature maintained in the 
test chamber was 700 ± 1°C. 
In a test of long duration, two chambers were used 
in series with refreshment (oxygen-saturated) water 
passing through each in turn. In this case, the rate 
of water flow was 15 cc/mm for the first 5 days and 
7 cc/mm thereafter. However, in some tests the rate 
of flow was increased to over 60 cc/min to determine 
the effect of the refreshment rate. 
Tests were conducted for periods of nearly 1000 
days. In some cases, specimens were temporarily re-
moved to determine the effect of exposure interrup-
tion. Also, the number of sample rods used in each 
test was varied from one to eight to determine what 
effect the amount of aluminum surface area had on 
the rate and amount of corrosion. 
The amount of corrosion was determined by an 
eddy current thickness gage which is insensitive to the 
oxide coating (corrosion). The change in the induction 
properties of a coil is used as a function of the thick-
ness of uncorroded metal placed within it. When 
properly calibrated, the gage measures the thickness 
of uncorroded metal to an accuracy of ±25 A. 
As a result of the study the following conclusions 
were reached:
The amount of corrosion during the first 7 hours 
of exposure is proportional to the logarithm of 
time. Exposure interruptions during the first 48 
hours resulted in a substantial reduction in subse-
quent corrosion rate (as compared to continuous 
exposure); however, interruptions after the first 
several days of a test resulted in no discernible 
effect to the corrosion rate. 
2. The number of specimens caused wide variances 
in the corrosion rate. Substantially more corrosion 
occurred per specimen in the chamber containing 
more corroding metal (more specimens), indicating 
that a product of the corrosion reaction contami-
nates the water and increases the corrosion. This 
was further indicated by the effect of the refresh-
ment rate. Higher flow rates diluted the contami-
nant that increases corrosion, reducing the rate 
of corrosion. In the case where a second test 
chamber was used, the corrosion rate was higher 
since contaminated water flowed into the second 
chamber while clean water flowed into the first 
chamber. 
3. During longer test periods, the initial corrosion 
was logarithmic and was followed by an increase 
in rate and by a subsequent extended period of 
logarithm reaction. From this it is assumed that 
the surface of the test sample develops a periodic 
logarithmic growth and breakdown of a protective 
oxide film. The breakdown is caused by a cor-
rosion product (hydrogen) which builds up enough 
pressure under the film to rupture it. Each time 
the breakdown of protective film occurs, the ini-
tial rate of reaction is less than that preceding 
the break. The total amount of corrosion occur-
ring in each cycle is the same; consequently, the 
duration of succeeding cycles is longer.
(continued overleaf) 
This document was prepared under the sponsorship of the Atomic liability resulting from the use of the information contained in this 
Energy Commission and/or the National Aeronautics and Space document, or warrants that the use of any information, apparatus, 
Administration. Neither the United States Government nor any per- method, or process disclosed in this document may not infringe pri-
son acting on behalf of the United States Government assumes any vately owned rights.
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4. On the basis of the test information, a corrosion 
rate expression was derived that fits the known 
observations. The derivation is a simple loga- 
rithmic equation of the form 
L = Ki + K21n t 
where L is the amount of metal corroded and t is 
time. 
Notes 
1. References: Jour. Electrochem. Soc. vol. 110, no. 6, 
June 1963. Corrosion, vol. 19, no. 8', p. 269t-271t, 
August 1963. Corrosion, vol. 19, no. 5, p. 165t-
168t, May 1963. Jour. Electrochem. Soc. vol. 114, 
352, 353 (1967).
2. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B67-10578 
Source: J. E. Draley, S. Mori, 
and R. E. Loess 
Metallurgy Division 
Patent status:	 (ARG10045) 
Inquiries about obtaining rights for commercial 
use of this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439 
Brief 67-10578	 Category 03


Study of corrosion of 1100 aluminum

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