Volume 6 Preprint 51
Investigating Potential Corrosion Associated with Newly Developed Fuels
Harovel G. Wheat and Mirage Thakar
Keywords: fuels, emulsified diesel fuel, corrosion, compatibility
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Volume 6 Paper C124
Investigating Potential Corrosion Associated with Newly
Harovel G. Wheat and Mirage Thakar, Mechanical Engineering
Department, University of Texas at Austin, 1 University Station, C2200,
Austin, TX 78712-0292, USA
As the search for fuels with reduced emissions continues, there is a
need to understand the corrosion behavior of newly developed fuels
and modified fuels when they are in contact with fuel tanks and
storage tanks. Traditionally these tanks have been made of steel or
coated steel. These fuels are usually not very conductive, so special
procedures are often required. Nevertheless, test procedures for the
study of fuels in steel containers currently exist. Recent legislation,
however, will require that the containers have increased life and
perhaps even lower weight. Therefore, new materials, which may be
nonferrous or even nonmetallic, may be required. This means that in
the future there may be new tanks and new fuels. It is therefore even
more important to develop a clearer understanding of the potential
interactions between the new tanks and the new fuels.
In this paper, a test procedure will be described for the study of the
corrosion behavior of new fuels in contact with new materials. Results
based on this methodology and newly developed fuels will be
These fuels provide emissions benefits in terms of the
oxides of nitrogen and particulate matter when tested over any cycle.
This paper will address the concern as to whether additives necessary
to cause the emissions reductions result in an increased corrosion risk.
Keywords: fuels, emulsified diesel fuel, corrosion, compatibility
Air pollution has become a cause of major concern in the last few
decades. In addition to techniques such as using catalytic converters,
efforts are being made to develop new fuels that will cause a reduction
in polluting emissions from vehicles. Emissions from diesel fuels seem
to be of particular concern. Several emulsified diesel fuels have been
developed in an effort to reduce NOx emissions and particulates.
These fuels are based on diesel fuels and thus would be expected to
behave in a similar manner to diesel fuels. However, there is some
concern about the compatibility of the new fuels with the existing
vehicle systems because of the additives that have been included;
additives that result in lower NOx emissions and particulates.
Therefore, the compatibility of these new fuels with containers such as
fuel tanks and storage tanks needs to be demonstrated.
The research described in this paper is part of a much larger project in
which performance, thermal properties, and other issues associated
with these new fuels are being examined. In this paper, the research
was aimed at identifying the corrosion behavior of some of these new
fuels and their compatibility with existing fuel tank materials.
Several known tests are available for studying the corrosion behavior
of fuels and/or petroleum products. Two tests in particular are SAE
J1747 DEC94, Recommended Methods for Conducting Corrosion Tests
in Gasoline/Methanol Fuel Mixtures and ASTM D130-94 Standard Test
Method for Detection of Copper Corrosion from Petroleum Products by
the Copper Strip Test. Both tests require elevated temperatures and
the latter one even requires a corrosion test bomb. Since very little is
known about the corrosion behavior of these new emulsified fuels, it
was decided to gain initial information by using a simplified approach;
essentially a planned interval test in which steel strips were immersed
in test tubes containing the fuel at room temperature as well as
immersion tests involving steel springs at elevated temperatures.
Prior to conducting the planned interval test, specimens made from
1018 steel and having dimensions 2.75 x 0.325 x 0.25 inch (69.85 x
8.25 x 6.35 mm) were immersed in the selected fuels to gain
information as to how the test procedure would be carried out. This
steel is a plain carbon steel containing 0.18 weight percent carbon and
the balance iron. Steels like this can be used in the construction of
automobile fuel tanks. The specimens were polished to a surface finish
of 600 grit using SiC paper. Three sets of specimens (each containing
7 steel strips) which had previously been weighed were completely
immersed in individual test tubes containing one of three fuels; a
typical diesel fuel which will be referred to as Fuel D, an emulsified
diesel fuel which will be referred to as Fuel S, and another emulsified
diesel fuel which will be referred to as Fuel W. In all there were 21
specimens. A cork was placed on each test tube and the test tubes
were kept in an upright position. They were not agitated during
exposure. Specimens were removed after one day, two days, etc up to
five days. The specimens were removed from the fuels and placed in
another clean, dry test tube so that the viscous fuel adhering to the
specimens could drip off. The next day, they were dried, weighed, and
stored in a dry container for examination at a later time.
In typical tests where metallic materials are exposed to salt water or
acids, the metallic materials are removed after some time and any
procedure and cleaning solution according to certain ASTM or other
standard guidelines. This is done prior to weighing the specimens to
observe the weight change (usually a weight loss), from which a
corrosion rate can be determined. However, in this case the fuel, which
is more viscous than most electrolytes, was allowed to dry before the
specimens were re-weighed. No solvent was used to remove the fuels.
The next set of experiments involved a planned interval test. The idea
was to determine the corrosion rate based on weight change and to
use that information to determine if the corrodibility of the metal
changes with time and if the corrosiveness of the electrolyte changes
The interval of time was taken to be one week and the
duration of the test was four weeks. Each test involved triplicate
In this test 9 specimens were placed in Fuel D, 9 were
placed in Fuel S and 9 were placed in Fuel W.
After 7 days, 3
specimens were removed from each fuel; after 14 days 3 more
specimens were removed from each fuel; and after 21 days the final 3
specimens were removed from each fuel.
In the fourth week, three
new specimens were placed in the used fuel from which three
specimens of the second set had been removed. They were removed
after 21 days of immersion.
The third set of experiments involved immersion of steel springs in the
fuels at 50 degrees C.
These springs are representative of vehicle
components that have undergone deformation prior to use.
known that certain types of springs are subjected to high temperatures
during vehicle operation and may experience failure due to corrosion.
Results and Discussion
The emulsified fuels, Fuel S and Fuel W, started showing signs of
separation after about 3 days and this separation progressed with
time. Separation is the process by which the white, denser part of the
emulsified fuel settles to the bottom and the lighter portion rises to
the surface. Figures 1 and 2 show the early fuel separation and the
progressive separation after about 40 days, respectively. In their
corrosion tests of stainless steels in methanol-based fuels, Lall and
Svilar (1) also found that test fuels containing 15% aggressive
methanol separated into two immiscible liquids. In addition, the liquid
on top tended to evaporate away very quickly.
Figure 1. Strips of 1018 steel completely immersed in the emulsified
Figure 2. Fuel separation after 40 days.
Even though the emulsified fuels experienced separation, there was no
visible evidence of corrosion in the specimens that were exposed to
Fuels S, W, and D for up to 5 days. In addition, the weight change was
negligible; on the order of micrograms or less for specimens which
initially weighed about 16 grams. In fact, in most cases, there was a
slight increase in weight, on the order of micrograms or less. This is
probably because no solvent was used to clean the specimens after
exposure and the fuels were allowed to drip off the specimens.
No evidence of corrosion was observed until at least three weeks of
exposure. Figure 3 shows evidence of corrosion extending upwards
from the separation interface after more than 30 days of exposure.
This finding is similar to observations noted by Lall and Svilar (1)
except that in their case, corrosion was observed only on the area of
the test samples that was immersed in the denser liquid.
Figure 3. Evidence of corrosion above the separation interface after
exposure for more than 30 days. Specimen No. 7 was immersed in
Fuel S for 31 days. Specimen No. 35 was immersed in Fuel W for 42
Specimens, which were removed from Fuels S and W, showed evidence
of corrosion at the bottom where the fuel accumulated as it dripped
Figure 4 shows a specimen with corrosion only on the bottom
portion. Specimens that were exposed to Fuel D, the diesel fuel,
showed no evidence of corrosion after periods of exposure similar to
those for Fuels S and W. Figure 5 shows specimens removed from Fuel
Figure 4. Specimen showing accumulation of fuel after removal from
Figure 5. Specimens after exposure to Fuel D for 42 days.
The results of the planned interval test after 14 days, 21 days, and 21
days (in used fuel), are shown in Figures 6, 7 and 8, respectively. The
time dependence is observable in the fact that there is essentially no
evidence of corrosion on specimens in any of the fuels after 14 days
(Figure 6). A period of about 21days was necessary to initiate the
corrosion process. In addition, the corrosion process in the used fuel
(the fuel that had separated) progressed at a faster rate. A comparison
of Figure 7 (21 days in new fuel) and Figure 8 (21 days in used fuel)
clearly demonstrates this.
Figure 6: Specimens 4, 5 and 6 after 14 days of exposure to Fuel S,
Fuel W, and Fuel D, respectively. (Note corrosion only at lower end due
to fuel accumulation after removal from exposure).
Figure 7: Specimens 7, 8 and 9 after 21 days of exposure to Fuel S,
Fuel W, and Fuel D, respectively.
Figure 8: Specimens 10, 11 and 12 after 21 days of exposure to used
Fuel S, W, and D, respectively.
The results of immersion tests of the steel springs were similar to
those observed in the planned interval test. However, with the higher
temperature, the corrosion process was accelerated. Figure 9 shows a
photograph of one of the springs before exposure. Because of their
larger size, they had to be placed in beakers rather than test tubes.
Figure 10 shows the separation in Fuels S and W. As observed before,
corrosion generally takes place above the separation interface. In this
case, due to more rapid separation, almost the entire spring is left
Photographs taken of the springs after 15 days of immersion in Fuels
S, W, and D are shown in Figures 11, 12, and 13, respectively. It is
interesting to note that at room temperature, about 21 days were
required to initiate corrosion, but at the higher temperature, corrosion
is starting about a week earlier.
Figure 9. Photograph of the steel springs before immersion
Figure 10. Photograph of beakers containing the springs in Fuel S and
Fuel W at 50ºC. (Note the fuel separation)
Figure 11. Springs removed from Fuel S after15 days at 50ºC.
Figure 12. Springs removed from Fuel W after 15 days at 50ºC
Figure 13. Specimens removed from Fuel D after15 days at 50ºC.
In the case of the particular steels and emulsified fuels used in this
investigation, the corrosion behavior seemed to be directly related to
fuel separation as evidenced by corrosion above the separation
interface. This suggests that differential aeration cells may play a
major role in the corrosion process. With respect to fuel/fuel tank
compatibility, this could mean that long periods of exposure
accompanied by fuel separation could be a problem.
It should be
pointed out that relatively long periods seem to be required at room
temperature, as no evidence of corrosion was obvious until about
three weeks. With respect to fuel/storage tank compatibility, there is
indication that the problem has already been addressed since the fuels
in storage tanks generally
undergo periodic agitation.
biocides are often used to mitigate microbiologically influenced
It should be noted that the corrosion behavior is very dependent on
the fuel/metal combination. Similar tests conducted on a plated steel
in Fuels S and W at 50 degrees C for 15 days showed no visible
evidence of corrosion. Lall and Svilar ( 1) also found that two of their
steels exhibited corrosion in 24 hours while certain austenitic stainless
steels showed less than 2% of the surface was covered in rust after
Based on this investigation, the results of the exposure of 1018 steel
(and presumably other similar steels) to two emulsified fuels, Fuel S
and W, at room temperature indicate that prolonged exposure could
be a potential problem.
Relatively long periods seem to be required at room temperature, as
no evidence of corrosion was obvious until about three weeks.
The problem seems to accompany fuel separation, since the corroded
surface seems to coincide with the extent of separation and the
corroded area is the area above the separation interface.
Corrosion rates based on weight changes after allowing the fuel to
drip off were very negligible.
When specimens were immersed in used emulsified fuels (fuel which
had been allowed to separate), the corrosion progressed at a faster
Corrosion required some time to initiate; in this case about 21 days.
The higher temperature of 50ºC resulted in faster separation of the
emulsified fuels and enhanced corrosion of springs after 15 days in
Fuels S and W.
The authors are very grateful to Dr. Ronald Matthews of the Mechanical
Engineering Department at the University of Texas at Austin and Mr.
Don Lewis of the Texas Department of Transportation.
1. Lall, C. and M. Svilar, “The corrosion resistance of p/m stainless
steels and selected alloys in methanol-based fuels,” Proceedings of the
1992 Powder Metallurgy Inst, San Francisco, June 21-26, 1992, Publ
by Metal Powder Industries Federation, Princeton, NJ, USA.