Research paper

1. Research J. Engineering and Tech. 6(4): October- December, 2015
455
ISSN 0976-2973 (Print) www.anvpublication.org
2321-581X (online)
RESEARCH ARTICLE
An Overview of Corrosion Performance of Automotive Metals in Biodiesel
Dr. C. Kavitha1
and P. Vijayasarathi2
1
Asst. Professor, Department of Chemistry, Jeppiaar Institute of Technology, Chennai, Tamil Nadu, India
631604
2
Asst. Professor, Department of Mechanical Engineering, Jeppiaar Institute of Technology, Chennai, Tamil
Nadu, India 631604
*Corresponding Author Email: ckavitha@jeppiaarinstitute.org, vijayasarathiprabakaran@gmail.com
ABSTRACT:
This paper reviews the significance of biodiesel over fossil fuel and its effects of corrosion on the engine parts
that come in contact with a biodiesel fuel. Biodiesel seemed to degrade due to auto-oxidation and presence of
moisture to secondary products that enhanced the corrosion rate. The problem related to the use of non-
compatible materials as engine parts for biodiesel-run vehicles is dual in nature. The engine part in contact with
the fuel is corroded as a result of fuel degradation, causing the fuel to go further off-specification. Biodiesel is
more susceptible to oxidation, microbiological attack and sensitive to temperature and humidity changes, which
cause variation in pH and water content. These conditions increase their corrosion and degradation effects on
materials comprised in the systems implemented. Therefore, this paper aims to provide an overview and analysis
of the challenges and the materials proposed for the biodiesel supply.
KEYWORDS: Biodiesel fuel, corrosion, Stainless steel, Aluminium, Steel, Copper.
1. INTRODUCTION:
The existing enlargement of the Indian economy has
escalated petroleum exigency, prices have surged,
hurting the economies of poor and developing countries.
In order to perk up the economic prominence, the
renewable, non toxic biofuel comes with many
advantages for the environment. Biofuel (abbreviation of
biorganic fuel, sometimes called agro fuel) is a general
name of fuels derived from renewable sources,
sometimes called biomass. Biomass is biological
material (plant and animal) from living or recently living
matter, such as wood, other numerous types of plants,
grass, algae (micro organisms) and organic wastes
(manure, etc.). Biomass is generated by plant life.
Utilization of biofuels has some benefits, such as
attenuation the dependency on fossil fuels, improvement
of air quality and reduction in greenhouse gas emissions,
easy available and renewable raw materials.
Received on 04.07.2015 Accepted on 28.08.2015
©A&V Publications all right reserved
Research J. Engineering and Tech. 6(4): Oct. - Dec., 2015 page 455-462
DOI:
Biodiesel is a biofuel suitable for use in compression
ignition (diesel) engines. It is composed of long-chain
fatty acid monoalkyl esters (FAME—RCOOCH3 or
FAEE—RCOOC2H5) derived from plant oils, animal
fats, microalgae, recycled greases and oils. Biodiesel is
produced through chemical process called
transesterification. This process consists of reacting the
oil or fat with a short chain alcohol, usually methanol, in
the presence of catalysts that may be acidic, basic or
enzymatic [1-3]. The result is a mixture of fatty acid
methyl esters (FAME) known as biodiesel.
Catalyst
Fat + Methanol Glycerol + Fatty acid methyl ester (FAME)
The main reason to convert the oil or fat into biodiesel is
to reduce its viscosity obtaining similar properties of
diesel. While biodiesel is a lipid-based fuel, diesel is a
mix of paraffinic, olefinic and aromatic hydrocarbons
derived from the processing of crude oil.

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2. CHARACTERISTICS OF BIODIESEL:
Biodiesel is a new kind of clean, safe, renewable, and
biodegradable engine fuel. It can serve as a potential
replacement for petroleum diesel fuel [4, 5]. The high
molecular organic acids containing 16 and 18 carbon
atoms (oleic, linoleic and palmitic acids) can be present
in biodiesel. The higher saturated fatty acid content
would cause higher oxidative and thermal stability.
Biodiesel is similar in properties to conventional diesel
fuel producing by distillation of crude oil. The boiling
point of biodiesel generally ranges from 330 to 357 °C
and of conventional diesel fuel from 180 to 370 °C at 1
atm. In contrast to diesel fuel, biodiesel contains no
sulphur. Emissions of CO, CO2, non-burned
hydrocarbons and particulates are reduced after
combustion of biodiesel comparing with conventional
diesel fuel. Emission of NOx is increased but can be
reduced by use of a catalytic converter. Rudolph Diesel
was the first who used peanut oil as fuel for his engine in
1900 year.
3. ADVANTAGES OF BIODIESEL:
Mello et al., [6] suggested that vegetable oils represent a
ready, renewable, and clean energy source that has
shown promise as a substitute to petroleum diesel for
diesel engines. Edible oils like soybean, rapeseed,
sunflower, and palm oil are being used for the
production of biodiesel. Kegl, et al., [7] reported that
mostly the advantages of biodiesel such as higher
lubricity than conventional fuels, biodiesel is 100%
renewable when the alcohol used in the synthesis process
is also renewable, it is biodegradable, non-toxic, has
higher flash point, and has superior potential to reduce
emissions, especially the particulate, CO, aromatic and
polyaromatic compounds, from the exhaust pipes of the
cars.
The advantages of biofuel are
(i) It is quite analogous to fossil based diesel fuel and
possesses characteristics similar to that of diesel.
(ii) It offers high cetane number and is almost free from
sulphur
(iii) Studies have revealed lower level of emission of
pollutants which are potentially harmful to human being,
with bio diesel.
4. OXIDATIVE NATURE OF BIODIESEL:
Besides being an eco-friendly fuel, biodiesel has some
unfavourable characteristics such as oxidative instability,
can provide slightly lower engine performances such as
engine power and torque and higher fuel consumption
[8-10].
Even though the main concerns associated with the
biofuel are
(i) Poor oxidation stability in storage,
(ii) Acid attack on fuel system components and
(iii) During the combustion of biofuel at the dynamic
conditions of temperature, load and pressure, it causes
corrosion of the fuel system components.
(iv) Biodiesel also ought to be of high purity for its
compatibility in CI engines. Therefore, incomplete
conversion or inadequate purification (by water washing
or other means) may result in impurities such as
glycerol, free fatty acids, alcohol, and catalyst, causing
deposits in the engine, corrosion, and ultimately failure
of the fuel [11].
Janun and Ellis have reported that water can also cause
hydrolysis of biodiesel that is composed of esters to fatty
acids, furthering corrosive. The water content in
biodiesel can convert the fatty acid alkyl esters
(biodiesel) to fatty acids through a reversible reaction.
The oxidative behaviour of biodiesel enhances corrosion
and wear of engine parts in contact with biodiesel [12].
Sarin et al., have described that during oxidation process,
the fatty acid methyl ester usually forms a radical next to
double bond and then quickly bonds with the oxygen
from air. This process may change the fuel properties
including viscosity, total acid number, density, iodine
value, pour point, cloud point etc. Increased acidity and
peroxide value as a result of oxidation reactions can also
cause the corrosion of fuel system components,
hardening of rubber components and fusion of moving
components [13]. Scendo has explained that in the
presence of oxygen, metal could easily be oxidized to
different oxides and later it forms different metal
compounds by further oxidation [14]. This is why in
most cases, biodiesel exposed metal surface shows
higher oxygenated species. In addition, the ester
molecules of biodiesel are more hygroscopic and polar in
nature [15, 16] as compared to diesel.
The oxidation stability of biodiesel is low, and it is
necessary to measure because it describes the
degradation tendency. The degradation is accelerated by
the air, humidity and UV radiation. The oxidation
products of biodiesel are peroxides, hydroperoxides,
mono-carboxylic acids (e.g. formic acid, acetic acid,
propionic acid and caproic acid), aldehydes, ketones and
alcohols. The presence of acids increases the total acid
number and potential issues of corrosion [17,18].
Torsner has explained the features that make biodiesel
more corrosive and a higher degradation potential than
diesel are the following [19]:
1. Biodiesel aging plays an important role, as well as
vegetable oils, it becomes rancid in a matter of weeks.
2. It has higher electrical conductivity.

3. Research J. Engineering and Tech. 6(4): October- December, 2015
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3. Dissolved water up to 10 times. This makes it more
prone to corrosion influenced by micro organisms,
besides causing the hydrolysis of esters.
4. As a solvent may accelerate the degradation of
polymers and elastomers, causing its swelling and loss of
mechanical properties.
However, biofuels have some disadvantages, mainly
their compatibility with materials which are widely used
in contact with conventional fuels. Based on the biofuel
handling and guidelines report, corrosive characteristics
of biofuel are important for long term durability of
storage tanks and pipelines.
5. CORROSIVE NATURE OF VARIOUS
METALS BY BIODIESEL:
A large variety of metals and non-metals are used as the
material of construction for the various components of
the fuel system. The main components of the diesel fuel
system that comes in contact with biodiesel are the diesel
fuel tank, fuel filter, lift pump, plunger pump, priming
pump, injection pump and the injection nozzles. In a
basic diesel fuel system, the fuel tank stores the diesel
fuel and lines deliver the pressurised fuel around the
system. The fuel filter removes abrasive and water
particles from fuel. Then it is sent to the lift pump and
then to the injection pump, by creating a pressure
difference. The injection pump delivers an accurate
amount of fuel under very high pressure. And then
through the injector nozzle, it sprayed to the combustion
chamber [20].
Cole and Sherman have described that the most of the
components of biofuel system are made up of ferrous
metals are steel and cast iron, non ferrous metals are
aluminium and copper alloy. While the non-metallic
substances basically include elastomers. And they have
reported that corrosion becomes an important aspect in
usage of biodiesel fuel because many of the engine parts
are composed of metals such as aluminium, copper and
its alloys, and stainless steel [21] that may be prone to
corrosion. Fazal et. al., [22] have explained that the
percent of aluminium in engine components includes
piston (100%), cylinder heads (70%), and engine blocks
(19%). Pumps and injectors are often composed of
copper and its alloys. Parts composed of stainless steel
include fuel filter, valve bodies, nozzle, and pump ring.
Fuel degradation varies with the specific metal used.
Based on the observation that biodiesel degrades through
moisture absorption, auto-oxidation, and microbial
attack during storage, Fazal et al. [22] tested corrosion of
aluminium, copper, and stainless steel in petro diesel and
palm biodiesel. The static immersion test conducted on
B100 and diesel was done at 80 ◦C for 600 and 1200 h
and an agitation rate of 250 rpm. The corrosion rate in
copper, aluminium, and carbon steel has been found to
be 0.586, 0.202, and 0.015 mils per year (mpy),
respectively in palm biodiesel. In diesel, the rate of
corrosion was less and found to be less than 0.3 mpy for
copper, less than 0.15 mpy for aluminium, and was
almost the same for carbon steel (0.015 mpy). Haseeb et
al. [23] dealt with compatibility issues of automotive
materials with biodiesel fuel. Biodiesel has been reported
to cause corrosive as well as tribological wear on the
metallic parts and elastomers in the engine. The
tribological contact leads to removal of metal from the
surface through abrasion, adhesion, corrosion, scuffing,
and additive depletion. This causes mechanical damage
to the surface of the metallic parts of the engine.
Automobile engines have three major types of materials:
ferrous alloys, non-ferrous alloys, and elastomers. The
ferrous and non-ferrous metallic parts undergo corrosion
through chemical/ electrochemical attack and wear after
coming into contact with biodiesel. A synergetic effect
of corrosion and wear is thus caused in the metallic
materials in contact with biodiesel. Ferrous alloys have
better compatibility with biodiesel than non-ferrous
ones. Copper alloys are more prone to corrosion than
ferrous alloys. Fluorocarbons, a new group of
compounds, have high resistance to corrosion. The
enhanced rate of corrosion has been attributed to higher
temperature and to the agitation of metal specimen in the
fluid provided during the test [22, 24]. The extent of
corrosion in biodiesel increases with the blend ratio and
oxidation due to its contact with atmospheric oxygen.
Biodiesel also has a strong tendency to absorb moisture
from the atmosphere and undergo hydrolysis or
hydrolytic oxidation. Oxidation of biodiesel or
hydrolysis of the fuel causes degradation of biodiesel
and corrosion of the steel-based container. Thus, the
vicious circle begins, with corrosion further resulting in
formation of sediments that get deposited on various
engine parts such as injectors and pumps. The flow of
the fuel to the engine is reduced, which results in a
pressure drop across filters [25]. Haseeb et al.[26],
explained that diesel engine components are made from
a variety of metals, non-metals, and elastomers. The
main parts of the engine/vehicle that come in contact
with fuel are fuel tank, fuel feed pump, fuel lines, fuel
filter, fuel pump, fuel injector cylinder, piston assembly,
and exhaust system. These engine/vehicle parts are made
of metallic (i.e., steel, stainless steel, copper, aluminium,
copper-based alloy, aluminium-based alloy, iron-based
alloy, gray-cast iron, specialcast iron, cast aluminium,
forged aluminium, sand-cast aluminium, die-cast
aluminium, and aluminium fiber) and non-metallic
materials (i.e., elastomer, plastics, paint, coating, cork,
rubber, ceramic fiber, and even paper). The fuel comes
in contact with the various engine parts and its
accessories at varying temperature, velocity, load,
sliding, and physical state. It has been found that either

4. Research J. Engineering and Tech. 6(4): October- December, 2015
458
the impurities in biodiesel or the deterioration of
biodiesel through oxidation enhances the corrosiveness
of the fuel. Hence, in this section it is presented as a
review of the literature where it has been assessed the
compatibility of biofuel with different materials.
5.1. Aluminium:
Diaz et al. appraise the consequence of canola biodiesel,
containing assorted levels of contaminants (residual
catalyst, methanol, glycerol and water) on pure
aluminium using electrochemical techniques. This study
showed that aluminium corrosion in biodiesel is
intimately correlated to the degree of purity of the
biofuel. Therefore, the quality is crucial to prevent
damage to the metal [27]. An assessment of aluminium
(99% commercially pure) corrosion in diesel and palm
biodiesel by static immersion was performed.
Aluminium experienced higher pitting corrosion in
biodiesel than that in diesel. The surface morphology of
aluminium strips showed a higher pitting corrosion value
for biodiesel (80% and 18%, respectfully) compared to
diesel (54% and 10%, respectfully) [22]. Ballote et al.
[28] used electrochemical techniques to determine the
effect of corrosion in biodiesel samples exposed to
aluminium during different stages of washing. The
corrosion process occurred in the same manner as if
aluminium was exposed to aqueous or ethanol alkaline
solution. The electrochemical measurements were done
by Potentiostat / Galvanostat in a three electrode cell.
During the initial wash, the open circuit potential (Eocp)
showed a high negative value (−600 mV), which might
have occurred due to reaction of aluminium with
biodiesel. Repeated washing of biodiesel by water
resulted in a positive of Eocp value, which was attributed
to the use of potassium hydroxide or sodium hydroxide
as homogeneous catalyst which forms Al(OH)3 as a
passive layer. The corrosion potential (Ecorr) was
negative (below −500 mV) through six washing cycles,
but increased to −50 mV after the seventh wash cycle.
The corrosion current density also decreased with the
number of wash cycles (from 10 nA/cm2
to 0.10
nA/cm2
). Kaul et al. [29] demonstrated that the
corrosion rates for aluminium exposed to biodiesel
produced from Jatropha curcas (Jatropha), Pongamia
pinnata (Karanja), Madhuca indica (Mahua), and
Salvadora oleoides (Salvadora) were 0.0784, 0.0065,
0.1329, and 0.1988 mpy, respectively. Chen et al. [30]
investigated the corrosion effect of the biodiesel and
bioethanol on seven kinds of common metallic materials
at room temperature through metal immersion tests.
Aluminium alloy surface turned into the corrosion spots
after being immersed in the bioethanol, whereas the
pitting corrosion showed on the surfaces of carbon steel
and cast iron with the biodiesel.
5.2. Steel:
Boonyongmaneerat et al. [31] studied that the bare steel
was highly prone to corrosion owing to degradation of
the fuel through oxidation and hydrolysis. Grainawi and
Jakab [32] was evaluated the corrosion rate of steel in
biodiesel and diesel-biodiesel blends using gravimetric
techniques, optical examination of pitting and
electrochemical characterization. Some of the samples
contained water to simulate the worst conditions. The
specimens were exposed to biodiesel and blends for a
period of 12 weeks at slightly elevated temperatures, to
simulate the conditions of a typical fuel tank for a period
of 12 months. The average corrosion rates calculated
from the gravimetric tests were below 0.04 mm/year,
indicating excellent corrosion resistance. Maru et al.
[33], analyzed the interaction between three fuels
(petroleum diesel and two types of biodiesel — soybean
and sunflower) and structural carbon steel ASTM A36.
Results highlighted weight loss of carbon steel exposed
to biodiesel was slightly higher than diesel. Moreover,
the soybean biodiesel proved to be less reactive to the
metal than the sunflower biofuel. These findings were
contrary with the general statement that biodiesel is inert
to carbon steel.
Kaminski and Kurzydlowski was performed an
investigation of the corrosion resistance of carbon steel
in a diesel oil solution containing different amounts of
fatty acid methyl ester (as the bio component) and micro
organisms. It was concluded that the corrosion rate of
steel A 765(IV) in the interface water-fuel is dependent
on the concentration of bacteria degrading fuel and on
forming of three-component system biofuel-esters-water
in environments with a high content of FAME. In the
presence of sulphate reduction bacteria (SRB), an
increase of the corrosion rate is observed [34]. Tsuchiya
et al. [35], tested a terne sheet of steel by immersion in
diesel and at a maximum of B5 at 80 °C. Terne sheet is a
Pb–8% Sn coated rolled steel sheet which is commonly
used to fabricate fuel tanks. After 500 h, it was observed
pitting corrosion on the material surface of the sample in
B2 and B5 blends. Steel is an alloy comprised mostly of
iron and has a carbon content ranging from 0.2 to 2.1%
by weight. The carbon content in the steel could be a
reason for its high resistance to corrosion due to the fact
that carbon has a high corrosion resistance. Steel has
been found to show high resistance to corrosion in
biodiesel blends as evidenced from electrochemical
impedance spectroscopy (EIS) [36]. However, Prieto et
al. [37] reported that biodiesel is more conductive
electrically compared to gasoline and diesel and may
cause galvanic metal corrosion in steel. Maru et al. [33]
tested strips of structural carbon steel (CS) and high
density polyethylene (HDPE) exposed to soyabean
biodiesel, sunflower biodiesel, and diesel using static
emersion tests (SET), observing weight loss, and

5. Research J. Engineering and Tech. 6(4): October- December, 2015
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observing the surface by optical, scanning electron, and
atomic force microscopy. The time span of the test was
between 60 and 115 days. Although the weight of the CS
strips did not change with exposure to biodiesel for 60
days, the soybean biodiesel was found to be more
compatible with carbon steel than sunflower biodiesel
and even diesel. The weight loss that occurred in carbon
steel after 115 days was quite low (around 10−5 g) and
only slightly higher in biodiesel. In a recent study, Fazal
et al. [38] tested the effect of corrosion on mild steel
dipped in biodiesel and diesel at temperatures of 27, 50,
and 80 ◦C. Corrosion rate increased with increasing
temperature in the diesel (B0) and biodiesel, especially
B50 and B100. The study of surface morphology of the
test coupons suggested that the depth attack was more
prominent with metal surfaces exposed to biodiesel than
those exposed to diesel. Elemental analysis of the metal
samples also revealed presence of oxygen on their
surfaces, which increased at higher temperature,
indicating oxidation of the metal surface. X-ray
diffraction (XRD) analysis revealed two phases in diesel
exposed metal: Fe(OH)3 and Fe2O3. In the biodiesel-
exposed metal, a new, third, Fe2O2CO3 phase was
observed in addition to Fe(OH)3 and Fe2O3. The
formation of the Fe2O2CO3 phase has been attributed to
absorption of water, oxygen, and carbon dioxide from
the atmosphere.
Cast iron forms a small concentration of Fe2O3 and Fe
(OH)2 in diesel while relatively higher amount of FeCO3,
Fe2O3, Fe(OH)2, Fe2(OH)2CO3 is formed in biodiesel.
The colour of biodiesel exposed cast iron was changed to
black-reddish rust from its original grey colour. It is
believed that the formation of FeCO3, Fe2O3, Fe(OH)2,
Fe2(OH)2CO3 causes black-reddish colour of cast iron
surface.[39]
5.3. Copper:
Corrosion characteristics of copper in palm biodiesel
have been assessed. Pitting corrosion and coloration
changes were observed in the surface of copper. The
colour is associated with the type of oxide species
formed. It was found a correlation between the biodiesel
concentration and corrosion rate [23]. Fazal et al. [22],
have studied and compared the corrosive characteristics
of petroleum diesel and palm biodiesel for automotive
materials. One of them was copper. It was found that
copper is very susceptible to attack by biodiesel (B100),
reflected by weight loss and corrosion rate measurement,
density of pits, and results from inductively coupled
plasma test. Also, it was determined that copper acts as a
strong catalyst oxidizing palm biodiesel. Currently, the
level of corrosion in biodiesel fuel is specified by the
‘copper strip corrosion test’ and determined by ASTM D
93 specifications [40]. A polished copper strip is
immersed in a specified volume of biodiesel for a
specific time and temperature. The copper strip is then
removed and washed. The color of the strip is then
assessed as per the ASTM standard [41]. However, the
‘copper strip corrosion test’ provides limited information
with respect to corrosiveness as it measures the level of
corrosion that will occur when copper is present as
metal. The level of corrosion also depends on the type of
alloy in contact with biodiesel fuel. In general, copper
alloys have been found to be more corrosive than the
ferrous alloys [42]. Sgroi et. al., was explained that the
oil burner filter components made of copper and copper
alloys were found to corrode in biodiesel, resulting in the
fuel being contaminated with copper ions. The copper
content increased from 0.1 to 21 ppm after 2 h contact
with the fuel when analyzed on Inductively Coupled
Plasma (ICP) [43]. The surface morphology of copper
strips showed a higher pitting corrosion value for
biodiesel (80% and 18%, respectfully) compared to
diesel (54% and 10%, respectfully).[23] The mechanism
of pitting corrosion has been proposed by Mankowski et
al. [44] stated that copper interacts with atmospheric
oxygen to form CuO/CuCO3 in the outer layer, followed
by Cu2O in the inner layer. The same mechanism occurs
in biodiesel that is rich in oxygen (approximately 11%
elemental oxygen). Fazal et al. [22] found that biodiesel
exposed to the various metal strips for 1200 h at 80 ◦C
changed color due to formation of metal oxide. While
copper carbonate yielded a pale green color in biodiesel,
red colored cuprite oxide was dominant in diesel.
Biodiesel was exposed to metal and heated with and
without copper. Several new products (i.e., acids, short
chain esters, and ketones) were formed with and without
copper. The biodiesel exposed to copper resulted in
formation of some new products such as 9-octadecenoic
acid, octanoic acid, nonanoic acid, hexadecanoic acid,
and 9-octadecanoic acid. The drawbacks of corrosion are
dual in nature as the change in fuel composition due to
corrosion results in degradation of fuel properties of the
biodiesel. Meenakshi et. al. [45] concluded that
corrosion rates of copper in Pongamia pinnata oil are
found to be higher than brass. Hu et. al., [46] concluded
that the corrosion effects of biodiesel on copper and
carbon steel are more severe than those on aluminium
and stainless steel. The corrosion rates of copper, carbon
steel, aluminium, and stainless steel in biodiesel are
0.02334, 0.01819, 0.00324, and 0.00087 mm/year,
respectively. The corrosion mechanism of biodiesel on
metals should mostly be attributed to the chemical
corrosion. The corrosion products were primarily fatty
acid salts or metal oxides.
XRD pattern obtained by Fazal et al., [39] on diesel
exposed copper surface indicates the presence of CuO,
Cu2O, Cu(OH)2 along with base metal. Biodiesel
exposed copper surface shows comparatively higher
concentration of CuCO3 along with other copper

6. Research J. Engineering and Tech. 6(4): October- December, 2015
460
compounds such as CuO, Cu2O, Cu(OH)2,
CuCO3.Cu(OH)2 etc.
5.4. Stainless steel:
Tang et al., was determined the microbial corrosion
resistance of stainless steel 304 in diesel, biodiesel and
blends (B5, B20, B35, B50) with the presence of bacteria
was determined. The results showed that stainless steel
304 in the biofuel environment is characterized with a
high corrosion resistance [18]. Fazal et al. [22], studied
the corrosion behaviour of stainless steel 316 in diesel
and palm biodiesel through immersion tests at 80°C. It
was concluded that stainless steel it is compatible with
biodiesel. In biodiesel-run engines, a high chrome
stainless steel has been used to make oil nozzles and was
found to be resistant to corrosion when exposed to
biodiesel [43]. Diana and Sonia [47] have concluded
that the corrosion effects on mild carbon steel are more
severe than those on stainless steel and Monel steel,
probably because of the chemical corrosion that is acting
more easily on the mild carbon steel surface because of
the reaction of the mild ferrous material with the species
from biodiesel. The corrosion rates of mild carbon steel,
stainless steel and Monel steel in biodiesel are 0.000514
mm/year, 0.000421 mm/year and 0.000045 mm/year.
5.5. Bronze:
Sgroi et al., [43] observed pitting corrosion on sintered
bronze filters in oil nozzle after 10 h of operation with
biodiesel at 70 °C. Haseeb et al. [23] evaluated the
corrosive effects of palm biodiesel to leaded bronze at
different blends with diesel, B0, B50 and B100. The
metallic material experienced higher corrosion rate with
the increasing of biodiesel concentration. Also, it was
suggested that the degree of corrosivity of biodiesel is
associated with an important parameter known as total
acid number, which reflects the amount of free fatty
acids present in the biofuel. Moreover, chemical
composition and the presence of unsaturated fatty acids
determine if it is more prone to oxidation. Corrosion
was observed on the bronze filter incorporated in the oil
nozzle after 10 h operation using biodiesel at 70◦
C.
Pitting corrosion was also observed after several hours of
operation with biodiesel fuel [43]. Geller et al. [48]
reported that copper and brass are prone to corrosion as
observed by weight loss through pitting and deposits
covering the surface. As these materials are slowly
corroded by the biodiesel, they leach tiny amounts of
copper and zinc atoms into the fuel itself. As a result,
they serve to catalyze the degradation of the biodiesel.
Biodiesel that has been contaminated in such a way, will
experience a dramatic reduction in shelf life, and will
often develop sludge or sediments in the fuel system of a
vehicle
5.6. Miscellaneous:
Torsner had mentioned that only metallic materials
compatible and recommended being used with biodiesel
are stainless steel and aluminium [19]. Materials like
brass, copper, zinc, bronze, lead and tin are incompatible
with biodiesel and can accelerate the biofuel
degradation, leading to the formation of insoluble
(sediments) and salts or gels when reacted with one of
the fuel components [49]. The effect of biodiesel fuel
made from rapeseed oil on the corrosion properties of
copper, mild carbon steel, aluminium and stainless steel
was studied and compared with those of diesel fuel. The
metals were immersed in the fuels at 60°C for 60 days. It
was observed that corrosive effects of biodiesel on
copper and carbon steel are more severe than those on
aluminium and stainless steel [50]. Lee et al., [51]
conducted an investigation on characterizing
microbiologically influenced corrosion in biodiesel (B5,
B20, B80, B100) and diesel with water content. They
found biodiesel had the highest propensity for
biofouling. Carbon steel (C1020), stainless steel
(SS304L) and aluminium (A5052) were the alloys tested.
Carbon steel showed passive behavior in B100 and
biodiesel-diesel blends, but active uniform corrosion in
diesel. Stainless steel remained passive in all exposures
while A5052 was susceptible to pitting corrosion. The
degradation of different automotive materials, copper,
brass, aluminium and cast iron in palm biodiesel was
investigated by static immersion test. Upon exposure to
palm biodiesel, the degradation order for the different
metals was: copper > brass > aluminium > cast iron.
Each metal presented higher degradation in biodiesel
than that in diesel [39].
Aquino et. al., [52] was conducted an evaluation of the
influence of natural light incidence and temperature in
the corrosion rate of brass and copper immersed in
commercial biodiesel. The tests were performed at room
temperature and 55°C in light presence and absence. The
results showed that both materials corroded with a higher
rate in the presence of light at higher temperature and
influenced by dissolved oxygen in the biodiesel.
Boonyongmaneerat et al. [31] studied that pure nickel
metal was found to offer a high corrosion resistance to
biodiesel and its vapours during the SIT. The nickel–
tungsten alloy showed high occurrence of corrosion in
just 1–2 months. After 3 months, water content of
biodiesel increased from 700 to 1800 ppm, which was
indicative of the water absorption capacity of biodiesel.
However, the acid value increased from just 0.8 to 1.1
mg KOH/g in the 2-month period. The absorption
solvent and the relaxation of polymer chains increased
mass and swelling of the nitrile rubber and
polychloroprene. Increased cross linking agent results in
more swelling. In polychloroprene, glycol
dimethacrylates present as cross-linking agent resulted in

7. Research J. Engineering and Tech. 6(4): October- December, 2015
461
lower swelling in fuels compared to nitrile rubber.
Swelling increased with increase in biodiesel content in
the fuel. Elastomers include polar as well as non-polar
substances. Thus, the polar end of the biodiesel (present
in esters) interacts with the elastomers through dipole–
dipole interaction, causing them to swell. This has been
attributed to higher liquid absorption as compared to the
extraction of soluble components from the elastomer.
Increasing temperature had varying effect on elastomers.
While increased swelling was observed in nitrile rubber,
decreased swelling was observed in polychloroprene and
almost no change was observed in fluoroviton A at 50◦
C.
The reason attributed for loss in mass and volume in
polychloroprene is its containing polychloroprene, which
is stable at low temperature and thus its polar group gets
dissolved in biodiesel, causing reduced weight and
volume. A decrease in tensile strength was observed in
nitrile rubber and polychloroprene. However, no change
in tensile strength was observed in fluoro-viton. Analysis
by FTIR spectrometry showed presence of carbon–
carbon double bonds that may have resulted from
reaction between the methylene or vinyl groups of nitrile
rubber. The degradation of nitrile rubber and
polychloroprene in biodiesel has been attributed to the
carboxylic polar groups present in biodiesel. Haseeb et
al. [53] tested the physical properties of various
elastomers on their exposure to diesel and biodiesel
(prepared from palm oil). When exposed to biodiesel,
elastomers are affected in two ways: first by absorption
of liquid by elastomers and second, by dissolution of
soluble components from the elastomers in the liquid
medium. Swelling was the result of high absorption
amount by elastomers in comparison to their dissolution
in the fuel.
6. CONCLUSION:
Based on the investigations carried out by the several
researchers, the following conclusions have been
summarized:
This review demonstrates that corrosion is higher with
biodiesel than fossil fuel. It is vital to ensure the
optimum performance of the equipment, machinery and
transport system involved along the biofuel supply chain.
Also, it is important to the development of official
regulations, which specify with precision the biofuel
compatible materials to be used. The metallic material
experienced higher corrosion rate with the increasing of
biodiesel concentration. The ferrous and non-ferrous
metallic parts undergo corrosion through chemical/
electrochemical attack and wear after coming into
contact with biodiesel. A synergetic effect of corrosion
and wear is thus caused in the metallic materials in
contact with biodiesel. Ferrous alloys have better
compatibility with biodiesel than non-ferrous ones.
Copper alloys are more prone to corrosion than ferrous
alloys. Upon exposure to biodiesel, the degradation
order for the different metals was: copper > bronze >
aluminium > cast iron. The corrosive effects of biodiesel
on copper and carbon steel are more severe than those on
aluminium and stainless steel.
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