Copper and brass are used in many economic sectors as electrical, construction, transport and others. From common household electrical wiring to boat propellers and from photovoltaic cells to saxophones, copper and its alloys are employed in a variety of end-uses. Copper tubing is now the standard material for potable water and heating systems in most developed countries. This is in part due to its bacteriostatic properties, or in other words due to the ability of copper to inhibit the growth of bacterial and viral organisms in water. Therefore, the corrosion resistance of copper and brass are important in defining the field of use as construction parts. This paper aims at investigating the comparative corrosion behavior of pure copper and brass in 3.5 % NaCl solution. The corrosion behavior of both type samples in 3.5% NaCl solution was investigated by the use of electrochemical methods as open circuit potential and linear polarization resistance measurements. The results show an improved corrosion resistance of pure copper sample in 3.5 wt. % NaCl solution as compared with brass sample

Eliza DĂNĂILĂ

Lidia BENEA

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 2 - 2016, ISSN 1453 – 083X 
 
 
 
COMPARATIVE CORROSION BEHAVIOR OF PURE COPPER AND 
BRASS IN 3.5% NaCl SOLUTION 
 
Lidia BENEA, Eliza DĂNĂILĂ 
Competences Center: Interfaces-Tribocorrosion-Electrochemical Systems (CC-ITES), Faculty of Engineering, 
Dunarea de Jos University of Galati, 47 Domneasca Street, RO-800008 Galati, Romania 
e-mail: lidia.benea@ugal.ro 
 
ABSTRACT 
 
Copper and brass are used in many economic sectors as electrical, 
construction, transport and others. From common household electrical wiring to 
boat propellers and from photovoltaic cells to saxophones, copper and its alloys are 
employed in a variety of end-uses. Copper tubing is now the standard material for 
potable water and heating systems in most developed countries. This is in part due 
to its bacteriostatic properties, or in other words due to the ability of copper to 
inhibit the growth of bacterial and viral organisms in water. Therefore, the 
corrosion resistance of copper and brass are important in defining the field of use 
as construction parts. This paper aims at investigating the comparative corrosion 
behavior of pure copper and brass in 3.5 % NaCl solution. The corrosion behavior 
of both type samples in 3.5% NaCl solution was investigated by the use of 
electrochemical methods as open circuit potential and linear polarization 
resistance measurements. The results show an improved corrosion resistance of 
pure copper sample in 3.5 wt. % NaCl solution as compared with brass sample. 
 
KEYWORDS: copper, corrosion rate, cyclic voltametry 
 
1. Introduction 
 
Corrosion process is certainly one of the most 
common causes of failure of engineered components 
and structures. The corrosion phenomenon leads to 
deterioration of the material (usually a metal) and its 
properties, being caused by the reaction of the metal 
with the environment. The corrosion behavior of the 
material depends on the environment to which it is 
subjected, and the corrosive action of an environment 
depends on the material exposed to that environment 
[1]. Therefore, it is very important to know the 
corrosion resistance of a material before being 
designed for a specific application. 
Copper tubes are used for plumbing, heating, 
air-conditioning and refrigeration systems which can 
be found in the residential, industrial or commercial 
installations. For several decades, copper has been 
used as a plumbing material for potable water 
distribution systems [2]. Also, copper alloys like 
brass are widely used in domestic water-distribution 
systems in valves, heat exchangers, pumps, heating 
components, plumbing fittings and plumbing fixtures 
[3]. Localized or pitting corrosion is recognized as 
one of the major problems, with copper tubing or 
brass failure in tap water being a major and ongoing 
problem in many countries [2]. 
The aim of the present work is to systematically 
study the comparative corrosion behavior on pure 
copper and brass. Different electrochemical 
techniques were explored and complemented by 
surface optical microscopy. 
 
2. Materials and methods 
 
An VoltaLab PGZ 100 potentiostat / galvanostat 
controlled by VoltaMaster software was used for 
electrochemical measurements. A conventional three-
electrode setup was used for electrochemical studies, 
in which a Pt-Rh grid served as the auxiliary 
electrode and an Ag/AgCl with KCl saturated 
solution (E = 200 mV vs. standard hydrogen electrode 
– SHE) as the reference electrode. The copper 
electrode and brass respectively served as the 
working electrode. The chemical composition of 
tested samples was 99.97 % for pure copper and the 
following Cu-57.8%, Zn-39.02%, Pb-2.99%, Fe-
0.19% for brass. Prior to the corrosion tests, the 
surfaces of the samples exposed to the solution were 
mechanically polished to a mirror finish by using SiC 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 2 - 2016, ISSN 1453 – 083X 
 
grinding paper (320-2000 µm), degreased with 
acetone and dried with hot air. The exposure surface 
area of the working electrode was 6.25 cm2. As the 
corrosive electrolyte was selected 3.5 % NaCl 
aqueous solution and electrochemical measurements 
were conducted at room temperature. The pH of this 
solution was 6.43. The volume for each experiment 
was 135 mL of 3.5 % NaCl aqueous solution. 
 
3. Results and discussion 
 
3.1. Open Circuit Potential (OCP) 
 
The open circuit potential measurements give 
the information about thermodynamic stability of the 
sample surface to electrochemical oxidation in a 
particular corrosive environment [4]. This potential 
may vary with time due to change in the oxidation 
tendency of the surface (oxidation, formation of the 
passive layer or immunity) [4-5]. Figure 1 shows the 
variation of the open-circuit potential (EOC) with time, 
for copper and brass electrodes immersed in 3.5 % 
NaCl aqueous solution, over a period of 60 minutes. 
The EOC of the pure Cu electrode stabilizes at a more 
positive value as compared with that of brass 
electrode reaching a mean value of -189 mV versus 
Ag/AgCl. On the other hand, the Ecorr of the brass 
electrode reached a more negative steady state value, 
revealing an average value of -205 mV versus 
Ag/AgCl. 
 
 
 
Fig. 1. Open circuit potential (EOC) for: (1) pure 
copper and (2) brass electrodes over a period of 
60 minutes, immersed in 3.5 % NaCl aqueous 
solution 
 
The both type of studied samples reach the 
steady states after approximatively 22 minutes from 
immersion and did not exhibit potential drops 
associated with surface activation during 60 minutes 
exposure in the 3.5 % NaCl solution. This kind of 
behavior strongly suggests that the native oxide films 
from the both studied surfaces are thermodynamically 
resistant to chemical dissolution in 3.5 % NaCl 
solution. 
Since the difference between the steady states 
revealed by both electrodes (pure copper and brass) is 
not so big, of only 16 mV, it could be assumed that 
the processes which occur, on the brass surface are 
mainly governed by copper. Similar observations 
have been made earlier for Cu–16%Zn–6.5%Al alloy 
as compared with pure copper and pure zinc 
immersed in borate buffer solution [6]. In other 
words, it can be said that Zn element has a little 
influence in defining the potential of the 
brass/solution interface. 
 
3.2. Linear polarization resistance (LPR) 
 
Linear polarization resistance (LPR) is a rapid 
response testing technique commonly used in 
material corrosion studies which allow the calculation 
of the corrosion rate. For this method, the tested 
material was polarized with a small overvoltage in the 
range of ±40 mV, relative to its Open Circuit 
Potential (OCP) and the resulting ("linear") current 
response was measured. The measured resistance is 
inversely related to the corrosion rate. The linear 
polarization resistance measurements were carried out 
at a scan rate of 5 mV/sec. 
The polarization resistance values of the both 
tested surfaces studied in 3.5 % NaCl solution are 
shown in Fig. 2. 
 
 
 
Fig. 2. The evolution of Rp values during 
immersion time of: (1) pure copper and (2) brass 
electrodes 
 
From Fig. 2 it can be seen that the lowest 
polarization resistance (Rp) value is attained by the 
brass electrode being equal to 0.46 kohm cm2, while 
the pure copper electrode reveals a mean value of 
polarization resistance equal to 1 kohm cm2. An 
increased value of polarization resistance for pure 
copper electrode means lower corrosion current 
density and therefore a lower corrosion rate, as 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 2 - 2016, ISSN 1453 – 083X 
 
compared with brass electrode as it can be seen in 
Fig. 3. 
Corrosion rate can be defined as the amount of 
corrosion loss per year in thickness. From Fig. 3 it 
can be seen that the lowest corrosion rate value is 
attained by the pure copper electrode being equal to 
0.082 mm/year, while the brass electrode reveals a 
mean value of corrosion rate equal to 0.164 mm/year. 
According with the data presented in Fig. 3 it can be 
clearly seen that the corrosion rate of brass shows a 
double value as compared with pure cooper electrode. 
The higher corrosion rate corresponding to brass as 
compared with copper can be attributed to the 
presence of zinc as an alloying element, which leads 
to the incorporation of ZnO (as the main oxidation 
product on Zn metal) in the passive layer. Similar 
results were reported earlier by Kosec et al. [7] who 
studied the electrochemical behaviors of copper, Cu-
10Zn and Cu-40Zn alloys and zinc in inhibited and 
uninhibited 0.5 M NaCl solution and by Valcarce and 
collaborators [8] who investigated the susceptibility 
to pitting corrosion of copper and 70/30 brass in 
artificial tap water with or without Pseudomonas 
fluorescens. 
 
 
 
Fig. 3. Variation of corrosion rate vs. exposure 
time for: (1) pure copper and (2) brass 
electrodes 
 
Corrosion resistance is certainly an important 
consideration in constructive parts as automotive 
screw machine components. Despite exposure to 
corrosive conditions, the constructive parts must 
continue to function, threads and fittings must 
continue to fit properly, and an image of quality 
should be maintained. Affected by corrosion, many 
constructive parts can conduct to system failure. 
 
3.3. Cyclic voltammetry diagrams (CV) 
 
The cyclic voltammetry was initiated from 
negative direction (-1.0 V vs. Ag/AgCl) to positive 
direction (+0.3 V vs. Ag/AgCl) with the sweep rate of 
5 mV/s. The scan direction was reversed after the 
anodic current reached + 0.3 mV vs. Ag/AgCl to form 
a complete cycle and the recorded diagrams for both 
copper and brass are presented in Fig. 4. 
 
 
 
Fig. 4. Cyclic voltammograms of (1) copper and 
(2) brass performed at 5mV/sec sweep rate 
during immersion in 3.5 % NaCl aqueous 
solution expressed versus Normal Hydrogen 
Electrode (NHE) 
 
As it is shown in Fig. 4 the shape of both 
voltammograms are similar, but the anodic current for 
brass is higher as compared with anodic current for 
copper. 
The reversed diagrams from positive to negative 
potentials is drawn under the direct diagram from 
negative to positive direction for copper as well for 
brass confirming the repassivation of both surfaces. 
The reactions taking place at specific potentials for 
copper and copper corrosion compounds (products) 
are presented in Fig. 5. 
 
 
 
Fig. 5. Specific corrosion reactions of copper on 
cyclic voltammograms of copper at different 
potentials expressed versus Normal Hydrogen 
Electrode (NHE) 
 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 2 - 2016, ISSN 1453 – 083X 
 
The shape of cyclic voltammograms for brass is 
similar with those of copper explained by the fact that 
the corrosion process of brass is dominated by copper 
corrosion reactions. 
For zinc corrosion in brass on cyclic 
voltammograms we did not identify the specific 
reactions of zinc in the measured potentials range, 
confirming that the entire corrosion process of brass 
in sodium chloride solution is dominated by copper 
reactions. 
 
3.4. Optical Microscopy 
 
The optical micrographs of copper and brass 
surfaces performed before and after the corrosion 
tests are shown in Figures 6 and 7. 
 
          
 
Fig. 6. Optical microscopy images of pure copper (a) before and (b) after corrosion experiments 
 
In Fig 6 (a) it is shown copper surface before 
corrosion with some polished tracks. After corrosion, 
the surface of copper is uniformly covered with a thin 
layer of copper corrosion products (oxides with 
different colors. 
 
          
 
Fig. 7. Optical microscopy images of brass (a) before and (b) after corrosion experiments 
 
The surface of brass from Fig 7 (a) before 
corrosion tests presents some polishing tracks but also 
some inclusions. After corrosion tests, Fig. 7(b) the 
surface of brass shows mainly a corrosion film 
product very similar to copper. The corrosion 
products of zinc are easily soluble, and being white, it 
is difficult to distinguish from other colored oxides of 
copper. 
 
4. Conclusions 
 
Corrosion of materials is a very important issue 
to consider when choosing a material that must 
operate in a specific environment. 
After evaluating the results of laboratory 
research work on the two types of materials, the 
following have been drawn. 
The free potentials values of pure copper are 
nobler than that for their alloy with zinc (brass), 
according to evolution of potential at immersion in 
3.5% NaCl solution. 
By assessing polarization resistance through 30 
linear polarization measurements and dimensional 
mass loss (mm / year) it was observed the same trend 
of best corrosion resistance of copper compared with 
brass. 
From cyclic voltammograms and specific 
corrosion reactions identified at specific potentials, it 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
No. 2 - 2016, ISSN 1453 – 083X 
 
was shown that even on brass surface the corrosion 
process is dominated by copper reactions. 
The optical microscope micrographs before and 
after corrosion tests confirm the above-mentioned 
conclusions. 
 
References 
 
[1]. Davis J. R., Corrosion: Understanding the basics, ASM 
International, p. 1-17., 2000 
[2]. Burstein G. T., Bia H., Kawaley G., The Persistence of 
Inhibition of Copper Corrosion in Tap Water, Electrochimica Acta, 
191, p. 247-255, 2016. 
[3]. Yohai L., Vázquez M., Valcarce M. B., Brass corrosion in 
tap water distribution systems inhibited by phosphate ions, 
Corrosion Science, 53, p. 1130-1136, 2011. 
[4]. Santana Jiménez Y., Tejera Gil M., Torrado Guerra M., 
Baltes L. S., Mirza Rosca J. C., Interpretation of open circuit 
potential of two titanium alloys for a long-time immersion in 
physiological fluid, Bulletin of the Transilvania University of 
Brasov, vol. 2, (51), p. 197-204, 2009. 
[5]. Choudhary S., Garg A., Mondal K., Relation between open 
circuit potential and polarization resistance with rust and 
corrosion monitoring of mild steel, Journal of Materials 
Engineering and Performance vol. 25(7), p. 2969-2976, 2016. 
[6]. Blanco M., Barragan J. T. C., Barelli N., Noce R. D., 
Fugivara C. S., Fernández J., Benedetti A. V., On the 
electrochemical behavior of Cu–16%Zn–6.5%Al alloy containing 
the β-phase (martensite) in borate buffer, Electrochimica Acta, 
107, p. 238-247, 2013. 
[7]. Tadeja Kosec, Ingrid Milošev, Boris Pihlar, Benzotriazole as 
an inhibitor of brass corrosion in chloride solution, Applied 
Surface Science, 253, p. 8863-8873, 2007. 
[8]. Valcarce M. B., de Sánchez S. R., Vázquez M., Localized 
attack of copper and brass in tap water: the effect of Pseudomonas, 
Corrosion Science, 47, p. 795-809, 2005. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Comparative Corrosion Behavior of Pure Copper and Brass in 3.5% NaCl Solution

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Comparative Corrosion Behavior of Pure Copper and Brass in 3.5% NaCl Solution

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