NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC basic OIL

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BRAZILIAN JOURNAL OF PETROLEUM AND GAS ISSN 1982-0593 
MUNIZ, C. A. S.; DANTAS, T. N. C.; MOURA, E. F.; DANTAS NETO, A. A.; GURGEL, A. “NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC BASIC OIL”. 
Brazilian Journal of Petroleum and Gas. v. 2, n. 4, p. 143-153, 2008. 
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NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC 
BASIC OIL 
 
1C. A. S. Muniz, 1T. N. C. Dantas, 1,2E. F. Moura, 
3A. A. Dantas Neto, 4A. Gurgel* 
 
1 Universidade Federal do Rio Grande do Norte (UFRN), Departamento de Química, Campus 
 Universitário, 59078-970, Natal, RN, Brazil. 
2 Faculdade Natalense para o Desenvolvimento do RN (FARN), CEP 59014-540, Natal, RN, Brazil. 
3 Universidade Federal do Rio Grande do Norte (UFRN), Departamento de Engenharia Química, 
 CEP 59072-970, Natal, RN, Brazil. 
4 Universidade Federal de Viçosa (UFV), Departamento de Química, CEP 36570-000, Viçosa, MG, 
 Brazil. 
 
* To whom all correspondence should be addressed. 
Address: Universidade Federal de Viçosa (UFV), Departamento de Química, CEP 36570-000, Viçosa, 
MG, Brazil. 
Telephone / fax numbers: +55 31 3899-3208 / +55 31 3899-3065 
E-mail: agurgel@ufv.br 
 
Abstract. Cutting fluids are lubricating liquids required in several industrial activities 
where metallic parts and engines are manipulated. Considering the vast amount of 
mineral oil produced in Northeastern Brazil, we have detected the need to better employ 
this resource. In this work, novel formulations were prepared using a naphtenic mineral 
oil and the following additives: emulsifying (A), anticorrosive (B), biocide (C) and 
antifoam (D) agents. The formulations were prepared by mixing the additives with the 
mineral oil, under conditions established by a 24 factorial planning. Acidity index and 
viscosity measurements provided the physicochemical characterization of the 
formulations. Oil-in-water (O/W) emulsions were also prepared with these novel 
formulations, and parameters like stability, corrosion degree, percentage of foam 
formed and microbiological resistance were investigated. The best results were obtained 
with maximal amounts of all additives, and were similar to or even better than those 
provided by some commercial fluids available. 
 
Keywords: basic naphtenic oils; cutting fluids; O/W emulsions; corrosion 
 
 
1. INTRODUCTION 
With the evolution and modernization of 
metal-mechanical industries, specific 
developments have required the need to 
formulate special lubricating fluids that meet 
the constantly changing market requirements. 
Cutting fluids are important elements in the 
industrial processes, used for example during 
metal cutting or general metalworking 
operations. They are very complex mixtures 
that differ according to the types of operation 
implemented and the chemical nature of the 
metals handled in the industry (Silliman, 1992). 
The formulations are conceived from two basic, 
distinct fluids, typically water (W) and oil (O), 
and may therefore be classified as one of two 
kinds: aqueous or nonaqueous. Fluids derived 
from oil-in-water (O/W) dispersions in the 
form of emulsions may also be prepared, and 
are commonly known as Soluble Oils. Unlike 
their denomination, these types of fluids are not 
water-soluble, but form emulsions in an 
aqueous environment, effectively dispersing oil 
within the continuous water phase (Menniti et 
al., 2005). 
Northeastern Brazil is considered as one of 
the most important regions that produce basic 
oils for lubricating fluids. These are basic 
mineral oils which are emulsified upon the 
addition of specific agents to water, in order to 
BRAZILIAN JOURNAL OF PETROLEUM AND GAS 
MUNIZ, C. A. S.; DANTAS, T. N. C.; MOURA, E. F.; DANTAS NETO, A. A.; GURGEL, A. “NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC BASIC OIL”. 
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particularly form O/W emulsions (Haglund and 
Enghag, 1996). The composition of the cutting 
fluids also comprises additives like 
anticorrosion, biocide and antifoam agents 
(Ashjian et al., 1999; Kobessho and 
Matsumoto, 1999; Misra and Sköld, 2000). The 
mineral oils are obtained from the distillation of 
petroleum. Their properties depend on the 
nature of the crude oil, whose composition is 
extremely variable but may be summarized in 
terms of a large number of hydrocarbons 
belonging to two main classes: paraffinic and 
naphtenic. 
The lubricating oils are largely used as 
cooling agents and to enhance the finishing of 
metal surfaces, to reduce the deterioration of 
tools and protect them against corrosion, and 
also as biostable cutting fluids (El Baradie, 
1996), possessing many advantages with regard 
to environmental equilibrium and health of 
personnel who handle equipments and 
machinery. 
Engine manufacturers actually indicate 
which lubricating fluid is better designed for 
use and maintenance of their equipment. 
However, this does not imply total suppression 
of problems related to longer life of equipments 
operating under forced production conditions. 
Periods of time are still required for lubrication 
and interruption of the operation of all 
equipment (Kobessho and Matsumoto, 1999). 
In view of this, we aimed to investigate the 
preparation and characterization of novel 
cutting fluids formulations using basic 
naphtenic oils, with the objectives of better 
using the mineral oil produced in our region 
and optimizing the incorporation of additives in 
the formulations tested. The main focus of our 
work was to improve the quality of the final 
fluid, as far as technical and environmental 
aspects are concerned, with beneficial effects 
on human welfare. 
 
 
2. EXPERIMENTAL 
 
2.1. Materials 
 NH-20: a hydrogenated naphtenic mineral 
oil, kindly provided by LUBNOR 
PETROBRAS (“Lubrificantes e Derivados 
de Petróleo do Nordeste”, Brazil). All 
pertinent analyses were carried out by 
LUBNOR according to standard methods 
developed by the American Society for Test 
Materials – ASTM D 4057 (ASTM, 2006). 
The physicochemical properties of the 
material are listed as follows. Aspect: 
translucent liquid; ASTM Color: L 0.5; 
Kinematic viscosity at 40ºC: 21.14 cSt 
(centistokes); Kinematic viscosity at 100ºC: 
3.608 cSt; Flash point: 164.1ºC; Fuidity 
point: -4.5ºC; Total acidity index: 
0.01 mg KOH/g; Ash content: < 0.0010% 
weight; Ramsbolton carbon residue: 0.05% 
weight; Corrosivity to copper, performed at 
100ºC for three hours: 1.0; Relative density 
20/4ºC: 0.9023; Total sulfur: 0.0580% 
weight; Aniline point: 71.0ºC; Aromatic 
carbon: 14.1%; Naphtenic carbon: 40.1%; 
Paraffinic carbon: 15.9%; Water content 
(Karl Fischer): 71 ppm; Refractive index at 
20ºC: 1.4974. 
The efficiency of the formulations prepared 
was assessed by comparing their properties 
with those of two typical commercial cutting 
fluids available: OP 38 (from Lubrax) and 
Dromus B (from Shell). The additives used in 
the formulations are described below. 
 The emulsifying agent (Miracema) is a 
medium molecular weight sodium sulfonate 
which is associated with emulsion 
stabilization. It can be used in the 
formulations of soluble oils designed for 
cutting and emulsification operations in the 
industry. Its physicochemical properties are 
listed as follows. Aspect: translucent liquid; 
Density at 25ºC: ranging between 
0.97 g·cm-3 and 1.05 g·cm-3; Viscosity at 
40ºC: between 500 and 6000 cSt; Acidity 
index: 1.0 mg KOH/g; Flash point: 175ºC. 
 The selection of the anticorrosion agent 
(Miracema), which is constituted of amides 
of carboxylic acids, was based on its ability 
to stabilize mineral oil emulsions. Its 
physicochemical properties are listed as 
follows. Aspect: viscous liquid; Density at 
25ºC: ranging between 0.99 g·cm-3 and 
1.01 g·cm-3; Viscosity at 100ºC: between 
160 and 200 cSt; Acidity index: between 25 
and 34 mg KOH/g; Flash point:180ºC. 
BRAZILIAN JOURNAL OF PETROLEUM AND GAS 
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 The biocide agent (Miracema) is a triazine 
derivative used in the formulation of cutting 
fluids. It does not contain heavy metals, 
phenols, mercury or arsenic compounds. 
With soft odor, it does not irritate human 
skin and is readily soluble in water, polar 
solvents and mineral oils. Furthermore, it is 
not chemically affected by anionic, cationic 
and nonionic surfactants. Its 
physicochemical properties are listed as 
follows. Aspect: translucent liquid; Density 
at 25ºC: between 1.14 g·cm-3 and 
1.16 g·cm-3; Refractive index at 25ºC: 
between 1.460 and 1.465; pH of a 0.1% 
aqueous solution: between 9.5 and 10.5; 
Flash point: 70ºC. 
 The antifoam agent (Lubrizol) is an organic 
antifoam agent based on polisiloxanes. It is 
mainly used as foam quencher in industrial 
lubricating oils. Its physicochemical 
properties are listed as follows. Aspect: 
whitish opaque liquid; Odor: soft; Density at 
25ºC: 1.05 g·cm-3. 
 
2.2. Methods 
 
2.2.1. Experimental Planning 
The need to simultaneously analyze the 
different parameters that affect a certain 
process assumes a distinguished role during 
implementation of many industrial projects. 
The optimization of systems, products and 
processes via traditional procedures is only able 
to establish the best experimental conditions to 
be used when a large number of experiments 
are carried out (Box and Behnken, 1960). In the 
following paragraphs, we describe the well-
elaborated experimental strategy adopted in this 
work. Although applied to this particular 
research, the methodology minimizes cost and 
number of assays involved in any experimental 
investigation, either in the industry or in a 
research and development laboratory, or even 
in academic works. 
When an experimental planning is 
developed, the maximal amount of information 
may be acquired from the system under study 
in a rational and economical way. The 
methodology is essentially applied in the 
examination of process variables and their 
effects on the properties of the final product. 
A complete factorial planning is indicated 
when the most important variables are known 
for any specific system. Moreover, it is 
required to quantitatively evaluate their 
influence upon the response of interest, as well 
as to detect any possible interaction between 
one variable and others. Before starting any 
assay, the first step is to choose the factors and 
responses of interest. A factor is defined as any 
variable that affects the phenomenon studied. 
Such influence is translated into a response 
function or experimental response, which is the 
investigated property, and may be qualitative or 
quantitative (e.g. temperature, concentration, 
color, purity, chemical composition, yield, 
etc.). This choice depends on the characteristics 
of the system under investigation (ASTM, 
2006; Box and Behnken, 1960). 
The next step is the specification of the 
levels at which the factors must be examined 
when carrying out the experiments. In a 
complete factorial planning, all assays must be 
performed with all possible combinations 
between the levels of the factors. In each assay, 
the chemical system is tested by setting a 
previously defined combination of levels. The 
list of combinations is known as the planning 
matrix, whose lines correspond to certain 
combinations of upper and lower levels for 
each factor. Normally, the upper and lower 
levels are identified by the symbols (+) and (–), 
respectively. The range that corresponds to the 
lowest and highest levels attributed is known as 
the experimental domain of the planning 
(Hahn, 1993). 
In general, with n1 levels for factor 1, n2 
levels for factor 2, ... , and nk levels for factor k, 
the planning will result a (n1 · n2 · ... · nk) 
factorial. The simplest planning is devised 
when all factors are studied at two levels only. 
Therefore, with k variables being controlled by 
the analyst, a complete two-level planning 
requires the realization of 2k different 
experiments (Hahn, 1993). 
The effects of the main variables and their 
interactions can be estimated using the 
difference between the means of the generated 
outputs. The statistical significance attributed 
BRAZILIAN JOURNAL OF PETROLEUM AND GAS 
MUNIZ, C. A. S.; DANTAS, T. N. C.; MOURA, E. F.; DANTAS NETO, A. A.; GURGEL, A. “NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC BASIC OIL”. 
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to these effects can be assessed, based on a 
certain confidence interval (for instance, 95%), 
employing the Student distribution or via 
analysis of normal graphs. 
The statistical method used to describe the 
outputs of a factorial planning is formulated in 
terms of the effects per unit factor variation. 
The dependence of the output analyzed (Y) 
with the experimental variables (xi) can be 
approximated to a polynomial expression 
(equation 1): 
 
ijiijii xxbxbbY ∑∑ ++= 0 (1) 
 
where b0, bi and bij are constants; xi represents 
independent variables and xij denotes the 
interactions thereof. 
The most elucidative way to grasp 
information from an experimental planning is 
by means of interaction or contour diagrams, 
typically in the form of surfaces or cubes that 
represent and allow interpretation of the 
relationships existing between the outputs and 
the factors studied. This will be shown in the 
Results and Discussion section of this article. 
 
2.2.2. Preparation and Physicochemical 
Characterization of the Formulations 
Novel cutting fluids formulations were 
prepared from factorial planning indications, 
whereby the effects of four variables were 
examined at two levels (24 planning). Besides 
the NH-20 naphtenic oil, the following 
additives were used in the formulations: one 
emulsifying agent (A), one anticorrosion agent 
(B), one biocide (C) and one antifoam agent 
(D). The procedure consisted in the previous, 
controlled addition of these constituents to the 
oil. The system thus obtained was submitted to 
mechanical stirring at a speed of 700 rpm for 
10 minutes, at room temperature (25ºC). The 
investigated variables are listed in Table 1, 
together with their respective variation levels. 
The complete list of level combinations 
realized with this factorial planning is 
presented in Table 2. All assays were carried 
out in replicate. 
In order to determine the acidity index (A.I.) 
of each sample, the indicator method was 
Table 1. Factors and levels examined in the factorial planning used in the 
preparation of novel formulations of cutting fluids. 
Factor Symbol Level Minimum Maximum 
Emulsifying agent A (–) 8.0% (+) 12% 
Anticorrosion agent B (–) 1.0% (+) 2.0% 
Biocide C (–) 0.5% (+) 1.0% 
Antifoam agent D (–) 0.5% (+) 1.0% 
 
 
Table 2. Experimental matrix of the 24 factorial planning used 
in the study of novel cutting fluids formulations. 
Assay Nº Variable / Factor Examined (Levels) A B C D 
1 – – – – 
2 + – – – 
3 – + – – 
4 + + – – 
5 – – + – 
6 + – + – 
7 – + + – 
8 + + + – 
9 – – – + 
10 + – – + 
11 – + – + 
12 + + – + 
13 – – + + 
14 + – + + 
15 – + + + 
16 + + + + 
BRAZILIAN JOURNAL OF PETROLEUM AND GAS 
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performed, according to the ASTM D 974 
standard method (ASTM, 2007). Viscosity 
measurements were carried out within a broad 
shear range in a Raak rheometer, ModelRS 
150, during 10 min, at a constant temperature 
of 40ºC (ASTM, 2004), since this is the 
temperature level normally used when 
operating with commercial fluids. 
 
2.2.3. Preparation and Characterization of the 
Emulsions 
Oil-in-water (O/W) emulsions were 
prepared with all 16 novel formulations 
obtained, with the following oil concentrations: 
5%, 15% and 30%. Other oil concentrations 
were also tested, but more representative, stable 
formulations were prepared only with the 
specific oil contents mentioned above. The 
procedure consisted in adding the additive-
enriched oil phase to the aqueous phase, both 
kept at room temperature (25ºC), manually 
stirring each mixture by performing 30 tube 
inversions (180º rotations). The emulsions were 
characterized as to their stability, percentage of 
foam formed, corrosion level and 
microbiological resistance. Subsequently, they 
were compared with emulsions prepared with 
commercial fluids. 
Stability Study: The stability of the 
emulsions was visually assessed during 24 
hours, at constant temperature (25ºC), as to 
phase separation, in graduated 100-mL test 
tubes (with 1-mL subdivisions) in the following 
oil concentrations: 5%, 15% and 30%. The 
results are given in terms of volumetric 
percentage of water that separates from the 
initial mixture (%vol water). 
Foam Percentage Study: In order to quantify 
the percentage of foam formation (%FF) in the 
emulsions, 58.5 mL of distilled water and 
1.5 mL of the cutting fluid were added to a test 
tube, which was stoppered and submitted to 
continuous stirring and 30 inversions at 180º, 
for 20 minutes. The temperature was kept 
constant at 25ºC. 
Corrosion Level Study: This study involves 
the examination of “stains” on a filter paper 
resulting from the corrosive action of the 
cutting fluids after dispersion in water over cast 
iron splinters, which are allowed to interact 
with the paper. An emulsion was prepared with 
5% of the fluid into a 100 mL graduated test 
tube. An amount of 1 g of the cast iron splinters 
was weighed over a filter paper already 
accommodated in a Petri dish. Then 2 mL of 
the emulsion under investigation were collected 
with a pipette and the iron splinters were 
uniformly moistened with the help of a plastic 
spatula. The Petri dish was covered and 
allowed to rest for 2 hours. After this period the 
iron pieces were discarded and the filter paper 
was softly washed out with tap water. After a 
swift treatment in acetone, the paper was 
allowed to dry at room temperature and the 
corrosion level was assessed by sight. The 
results can be examined in terms of the 
pictorial representation shown in Figure 1 and 
the guidelines listed in Table 3. 
Microbiological Resistance Study: The 
microbiological resistance of the emulsions was 
examined according to the following 
procedure: 6 g of the cutting fluid were 
weighed in a glass container and 194 mL of 
water were added. The mixture was stirred and 
an emulsion formed. A total of 50 g of 
commercial corn flour, used as culture medium, 
was separately weighed. The emulsion was 
carefully poured over the flour, without 
stirring, and the pH was probed as a function of 
time (in days). 
 
 
3. RESULTS AND DISCUSSION 
Initially, sixteen novel formulations were 
prepared according to the 24 factorial planning 
presented in Tables 1 and 2. After 
 
 
Figure 1. Aspects of the filter paper after corrosion assays according to the corrosion levels detected. 
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characterization, O/W emulsions were prepared 
and the following assays were carried out: 
stability, foam formation, microbiological 
resistance and corrosion level. 
 
3.1. Physicochemical Characterization of the 
Formulations 
All 16 formulations were prepared with the 
additives kindly provided by the Brazilian 
companies Miracema and Lubrizol. Aiming to 
study the best composition for these 
formulations and the efficiency of the additives, 
the factorial planning was designed upon 
examination of four main components related 
to the final fluid composition, namely the 
emulsifying agent (A), the anticorrosion agent 
(B), the biocide (C) and the antifoam agent (D), 
in two concentration levels: maximal (+) and 
minimal (–), as shown in Tables 1 and 2. These 
values were selected based on the technical 
data sheet of the additives. The assays were 
replicated in order to enhance the statistical test 
and acquire a more representative model 
equation. 
After preparation of each sample, the 
resulting physicochemical property was 
measured according to the proper technique 
(see Experimental section). Table 4 
summarizes these results (A.I. and viscosity 
values). It must be emphasized that the values 
of acidity indices and viscosity must be 
compared with those of the commercial fluids 
tested, in order to better design their 
applications. This will be discussed later in this 
article. 
 
3.2. Analysis of Isoresponse Curves – Model 
Optimization 
The results for each assay (presented in 
Table 4 as a matrix) can be also expressed in 
terms of an experimental output or response Y, 
relative to each property investigated in this 
Table 3. Evaluation of the corrosion level developed after emulsion application 
on test filter paper surfaces (see text and Figure 1 for details). 
Corrosion Level Meaning Aspect of the Filter Surface 
0 No corrosion Unaltered or “stainless” 
1 Little corrosion Up to three corrosion spots, with average 
diameter lower than 1 mm 
2 Slight corrosion Stains covering less than 1% of the filter paper 
surface, but presenting a higher number of stains 
than those established for Level 1 or with 
average size higher than 1 mm 
3 Moderate corrosion Stains covering between 1% and 5% of the 
surface of the filter paper used 
4 Severe corrosion More than 5% of the paper surface affected 
 
 
Table 4. Physicochemical properties of the cutting fluids prepared. 
Assay or Sample A.I. / (mg KOH/g) Viscosity / cSt 
1 1.33 25.3 
2 0.65 27.3 
3 0.99 27.1 
4 1.01 28.8 
5 0.66 27.8 
6 0.99 28.7 
7 1.32 29.9 
8 1.33 31.5 
9 0.66 26.5 
10 1.00 26.7 
11 1.01 27.9 
12 0.99 29.9 
13 0.66 20.9 
14 0.67 28.7 
15 1.33 22.9 
16 1.32 34.3 
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work. Mathematical models were generated for 
each response, and the properties acidity index 
(A.I.) and viscosity could be evaluated. These 
correspond to the response Y. Maximization of 
the fitting models was performed via analysis 
of isoresponse curves that reflect the behavior 
of the variables within the studied domain. This 
was done after statistical analysis of the 
selected variables, attempting to verify their 
relative importance and possible interactions. 
The isoresponse curves are useful in inspection 
searches for acidity index and viscosity values 
that result in the highest fluid efficiency, and 
provide information on how these properties 
are altered along all composition points of the 
domain within which the formulations can be 
prepared. 
The optimized model equations are listed 
below (equations 2 and 3). The coefficients of 
the equations were determined via a multiple 
linear regression, together with variance 
analysis using the software Statistica 5.0. Note 
that, in equation 3, the isolated influence of 
variable D (antifoam agent) is not relevant on 
the final viscosity value. Further explanation on 
the variables that definethese equations is 
provided below. 
 
BCCBIAY 7560.08134.02268.08496.0.).( +++= (2) 
ADAityVisY 0872.2.00750.31355.29)cos( ++= (3) 
 
Figure 2 shows these curves in terms of 
acidiy index and viscosity, constructed with the 
optimized model as a function of variables A, 
B, C and D. The surfaces are plotted based on 
equations 2 and 3 above. In the A.I. study 
(Figure 2a), the concentrations of components 
A and D were fixed at their higher levels whilst 
concentrations of components B and C were 
varied; in the viscosity study (Figure 2b), the 
concentrations of components B and C were 
maintained at their higher levels, whilst 
changing concentrations of components A and 
D. All possible combinations between variables 
and responses were also assessed, but the 
approach mentioned above corresponds to the 
best results obtained in terms of minimization 
of the acidity index and viscosity, which is 
required in technological applications with the 
fluids formulated. 
Upon inspection of the isoresponse curves 
shown in Figure 2, two trends could be 
established, in particular: 
 With regard to the acidity index, when the 
concentrations of components A and D are 
fixed at their higher levels (12% and 1%, 
respectively), lower A.I. values are reached 
with decreasing concentrations of the 
anticorrosion agent (B) and increasing 
amounts of the biocide (C); 
 With regard to viscosity, when the 
concentrations of components B and C are 
fixed at their higher levels (2% and 1%, 
respectively), lower viscosity values are 
reached with decreasing concentrations of 
the emulsifying agent (A) and increasing 
amounts of the antifoam agent (D). 
The values of acidity indices of the novel 
formulations, presented in Table 4 and plotted 
in Figure 2, are lower than those of the 
commercial fluids tested (see discussion later in 
section 3.4), due to the anticorrosion agent used 
 
 
Figure 2. Isoresponse surfaces generated by the factorial planning with the novel formulations 
tested: (a) acidity index results; (b) viscosity results. 
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(B) being classified as an amine compound. 
This is in good agreement with reports in the 
literature that suggest that chemicals featuring 
amine moieties are potentially good metal 
corrosion inhibitors (Abd El Rehim et al., 
2003). Investigations on novel corrosion 
inhibiting agents or chemical systems has also 
been the objective of some works developed by 
our research group in recent years, with 
particular focus in self-assembling, surfactant-
containing systems (Dantas et al., 2002). 
On the other hand, the desired lower values 
of viscosity are only attained when components 
B and C are fixed at their higher levels and 
components A and D are varied, which is 
interesting when developing novel cutting 
fluids formulations. Fortunately, it will be 
demonstrated that the viscosity values of all 
novel formulations are lower than those of 
commercial fluids used, due to the chemical 
nature of the additives used in their 
composition (section 3.4). 
 
 
3.3. Properties of the Emulsions prepared 
with the Formulations 
 
3.3.1. Stability Study, Foam Formation and 
Corrosion Level 
Table 5 resumes the results of tests on 
stability (as to percentage of water separation), 
corrosion level and potential for foam 
formation (%FF) of the samples prepared with 
the novel formulations. It must be pointed out 
that the oil-in-water emulsions were prepared 
with concentrations of 5%, 15% or 30% in oil. 
Details on the experimental procedure carried 
out to perform such assays were given in 
section 2.2.3. 
With regard to the stability tests, the data in 
Table 5 referring to the 5% emulsions reveal 
that only samples 6, 8 and 16 were stable after 
24 hours. When 15% emulsions are analyzed, 
only sample 16 could remain stable and the 
other samples presented between 89% and 97% 
of water separation. At 30% oil content, 
samples 3, 6, 8, 11 and 16 could be stabilized, 
and the other samples allowed for percentages 
of water separation between 70% and 95%. It 
can be concluded that the acidity of the 
anticorrosion agent has an important effect on 
the emulsions stability, in that, upon increasing 
the concentration of this component in the 
medium, the final emulsions are destabilized. 
Table 5 also demonstrates that more stable 
emulsions, which lead to the separation of less 
amount of water, are prepared when the 
maximal concentration of components A, B, C 
and D are used. Sample 16 was the only one 
that remained stable at all oil concentrations. 
When considering the level of corrosion 
promoted, only slight to moderate levels were 
detected. The samples that induced the 
formation of moderate corrosion were 6, 8, 10, 
 
Table 5. Results of stability tests, corrosion level and potential foam 
formation for the novel formulations. 
Sample Stability Tests / (%vol water) Corrosion Level %FF 5% Emulsion* 5% Emulsion* 5% Emulsion* 
1 94 89 76 2 0.0 
2 97 89 80 2 3.3 
3 97 90 0 2 0.0 
4 96 90 85 2 3.3 
5 93 89 72 2 0.0 
6 0 97 0 3 0.0 
7 92 89 70 2 0.0 
8 0 94 0 3 0.0 
9 94 91 85 2 0.0 
10 95 92 78 3 0.0 
11 97 93 0 2 0.0 
12 94 94 95 2 0.0 
13 94 90 72 2 0.0 
14 97 96 92 3 0.0 
15 93 90 73 2 3.3 
16 0 0 0 3 0.0 
(*) The percentages correspond to the oil content in the oil-in-water emulsions prepared for these assays. 
BRAZILIAN JOURNAL OF PETROLEUM AND GAS 
MUNIZ, C. A. S.; DANTAS, T. N. C.; MOURA, E. F.; DANTAS NETO, A. A.; GURGEL, A. “NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC BASIC OIL”. 
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14 and 16. These must be compared with the 
levels promoted by the commercial fluids 
(moderate or severe, see section 3.4 below). 
This shows that the novel formulations are 
advantageous over the commercial fluids 
tested, and their performance is explained in 
terms of their composition, comprising 
aminated anticorrosion agents. The corrosion 
levels are therefore reduced with the novel 
formulations, which is a major requirement in 
technological applications where cutting fluids 
are to be in contact with metal surfaces. 
Finally, excellent results were obtained in 
the tests of foam formation with most 
formulations (13 out of 16 samples with 0.0% 
foam formation). Exceptions were observed 
with samples 2, 3 and 15, which presented only 
3.3% in foam formation. 
 
3.3.2. Microbiological Resistance of the 
Emulsions 
Table 6 shows the results of the 
microbiological resistance tests carried out 
according to the method described in section 
2.2.3. It can be seen that only samples 5, 6, 7, 
8, 13, 15 and 16 were able to maintain their pH 
values above 6.0 for five consecutive days 
(data in bold characters), which is required in 
other to avoid microbiological contamination. 
The pH values for the other samples were 
reduced, a reflection of microbiologically 
unstable emulsions. In this case, acidity is an 
indication of adulteration due to bacteria 
multiplication. Furthermore, it must be 
emphasized that the concentration of biocide 
(component C) was used in its higher level to 
prepare the samples listed above. This must be 
accounted for when attempting to correlate the 
microbiological resistances of the formulations 
and those of the commercial products, in that 
only by using the higher-level concentration of 
the biocide can the formulations be effective 
for longer. 
 
3.4. Comparative Study between the Novel 
Formulations and Commercial Cutting 
Fluids 
With the purpose of examining the potential 
applicability of the formulations prepared, a 
comparative study on theirproperties was 
carried out based on two commercial fluids 
available: OP38 (Lubrax) and Dromus B 
(Shell). Table 7 presents their specification in 
terms of acidity index, viscosity, emulsion 
stability, corrosion level, percentage of foam 
formed and microbiological resistance. Table 7 
also lists the same results obtained with 
samples 8 and 16, which were considered as 
more efficient among the 16 formulations 
tested, so as to allow for better comparison. 
An interesting result of this work refers to 
the lower viscosity values of the novel 
formulations, as effected by the 
physicochemical characteristics of the additives 
 
Table 6. Microbiological resistance results in terms of pH variation with time for 
the novel formulations tested. 
Sample / 
Assay 
pH 
1st Day 2nd Day 3rd Day 4th Day 5th Day 6th Day 
1 8.76 7.47 7.12 5.50 4.70 3.80 
2 8.15 7.74 7.05 5.96 5.02 3.60 
3 8.54 7.95 7.45 5.07 4.21 3.03 
4 8.77 8.29 7.84 5.11 4.70 3.20 
5 9.05 8.82 7.41 7.01 6.70 5.50 
6 9.28 8.64 8.45 8.04 7.77 5.03 
7 9.05 8.76 8.33 8.01 7.05 5.10 
8 8.97 8.50 7.82 7.30 7.02 4.55 
9 8.83 8.08 7.61 6.81 5.26 4.16 
10 8.92 8.12 7.68 5.53 4.09 3.50 
11 8.84 8.02 7.33 5.30 4.30 3.20 
12 9.09 8.07 7.67 5.07 4.15 3.70 
13 9.15 8.39 8.14 7.30 6.86 5.70 
14 8.86 8.30 7.51 6.95 5.65 4.36 
15 8.92 7.96 7.89 7.08 6.30 4.78 
16 9.10 8.59 8.08 7.84 6.45 4.80 
BRAZILIAN JOURNAL OF PETROLEUM AND GAS 
MUNIZ, C. A. S.; DANTAS, T. N. C.; MOURA, E. F.; DANTAS NETO, A. A.; GURGEL, A. “NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC BASIC OIL”. 
Brazilian Journal of Petroleum and Gas. v. 2, n. 4, p. 143-153, 2008. 
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used in their preparation. According to Table 7, 
the values of acidity index for the commercial 
fluid Dromus B were similar to those of the 
formulations, but the OP 38 fluid differs 
markedly. Emulsions prepared with 
commercial fluids are generally stable in the 
5% concentration level. With increasing oil 
content (15% and 30%), however, the systems 
are destabilized. This is not quite the case when 
the novel formulations are assayed: with 5% 
oil, samples 6, 8 and 16 form stable systems; 
this occurs only with sample 16 when 10% oil 
are present; when 15% oil is used, it is possible 
to prepare stable mixtures in a broader range of 
formulations (samples 3, 6, 8, 11 and 16). 
In view of the high percentage of foam 
produced, the commercial fluids are not 
satisfactory when compared to the novel 
formulations, which featured excellent results 
in terms of the very low amount of foam 
formed. Most formulations actually exhibited 
no foam upon agitation. Moreover, the 
commercial fluids are more susceptible to 
microbiological attack than the formulations 
tested, and lower corrosion levels are attained 
when the latter are used. This is attributed to 
the fact that the anticorrosion agent (B) used in 
the formulations is an aminated base. Overall, 
the results presented in this article clearly 
indicate that it is possible to prepare novel 
cutting fluid formulations that show better 
performance in technological applications 
when compared to common fluids already 
available in the market. 
 
 
4. CONCLUSIONS 
The main contribution of this work was to 
successfully demonstrate that novel cutting 
fluids formulations can be prepared using the 
basic naphtenic oil commonly known as NH-20 
and some specific additives, in various 
compositions. The quality of these formulations 
was examined by performing physical and 
chemical analyses, namely acidity index, 
viscosity, stability assays, percentage of foam 
formation, microbiological resistance and 
corrosion level. They have proven to be very 
satisfactory in terms of the excellent results of 
the analyses, as compared to two commercial 
fluids available. 
In particular, the following general 
conclusions are to be mentioned: the role of the 
anticorrosion agent used in the novel 
formulations was decisive to protect metallic 
surfaces, an aspect that was not so well 
accounted for with the commercial fluids, 
which may actually induce the formation of 
severe corrosion pits on metallic surfaces; the 
viscosity values of all novel formulations were 
within the accepted range established for 
optimal cutting fluids, and quite lower than the 
viscosities of the commercial fluids tested as 
comparison; good stability of oil-in-water 
emulsions prepared with the novel 
formulations, with different oil contents, was 
observed when the main constituents used 
(emulsifying agent, anticorrosion agent, biocide 
and antifoam agent) were employed at their 
higher concentration levels, according to the 
experimental planning devised for this work; 
practically no foam was generated with these 
formulations upon agitation; microbiological 
assays indicated that the pH of the emulsions 
remained above the levels required to avoid 
biological contamination over a longer period 
of time, which was not the case with the 
commercial fluids tested. 
Table 7. Specification of some commercial cutting fluids available compared with two of the novel 
formulations tested. 
Parameter Sample 8 Sample 16 OP 38 (Lubrax) 
Dromus B 
(Shell) 
Acidity index / (mg KOH/g) 1.00 1.33 4.80 0.65 
Viscosity at 40ºC / cSt 31.5 34.3 42.5 39.8 
Emulsion stability at 5% 0 0 0 0 
Emulsion stability at 15% 97 0 99 99 
Emulsion stability at 30% 0 0 98 97 
Corrosion level 3 3 4 4 
% Foam formed 0.00 0.00 15.00 8.33 
Microbiological resistance / days 5 5 2 2 
BRAZILIAN JOURNAL OF PETROLEUM AND GAS 
MUNIZ, C. A. S.; DANTAS, T. N. C.; MOURA, E. F.; DANTAS NETO, A. A.; GURGEL, A. “NOVEL FORMULATIONS OF CUTTING FLUIDS USING NAPHTENIC BASIC OIL”. 
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The enhancement of the performance and 
stability of cutting fluids helps to comply with 
market requirements and specifications. It is 
thus expected that this work prompts the 
diversification of researches on the continuous 
development of novel cutting fluids 
formulations, hopefully featuring better 
properties than the commercial products 
already available. 
 
 
ACKNOWLEDGEMENTS 
The authors are grateful to LUBNOR 
(Lubrificantes e Derivados de Petróleo do 
Nordeste, Brazil), Miracema-Nuodex Indústria 
Química Ltda. and Lubrizol do Brasil Aditivos 
Ltda., for supplying chemical samples, and 
CAPES (Coordenação de Aperfeiçoamento de 
Pessoal de Nível Superior, Brazil) for financial 
support. 
 
 
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