nano and corrosion

1. Supervisor:
Assistant. Prof. Dr. Ali Sabea Hammood
University of Kufa -Faculty of Engineering-Materials Engineering Department
Iraq

2. What are Nano-materials?
Nanoscale materials are defined as a set of
substances where at least one dimension is less
than approximately 100 nanometers. A
nanometer is one millionth of a millimeter
approximately 100,000 times smaller than the
diameter of a human hair. Nanomaterials are of
interest because at this scale unique optical,
magnetic, electrical, and other properties
emerge. These emergent properties have the
potential for great impacts in electronics,
medicine, and other fields

3. Fig. 1. Evolution of science and technology and
the future

4. Fig. 2. Nanomaterial (For example: Carbon nanotube)

5. Classification of Nanomaterials
Nanomaterials have extremely small size which having at least one
dimension 100 nm or less. Nanomaterials can be nanoscale in
one dimension (eg. surface films), two dimensions (eg. strands
or fibres), or three dimensions (eg. particles). They can exist in
single, fused, aggregated or agglomerated forms with spherical,
tubular, and irregular shapes. Common types of nanomaterials
include nanotubes, dendrimers, quantum dots and fullerenes.
Nanomaterials have applications in the field of nano technology,
and displays different physical chemical characteristics from
normal chemicals (i.e., silver nano, carbon nanotube, fullerene,
photocatalyst, carbon nano, silica). According to Siegel,
Nanostructured materials are classified as Zero dimensional, one
dimensional, two dimensional, three dimensional
nanostructures.

6. Fig. 3. Classification of Nanomaterials (a) 0D spheres and
clusters, (b) 1D nanofibers, wires, and rods, (c) 2D films, plates,
and networks, (d) 3D nanomaterials.

7. Examples of Nanomaterials
Nanomaterials (gold, carbon, metals, meta oxides and alloys)
with variety of morphologies (shapes) are depicted in Fig. 4.
Au nanoparticle Buckminsterfullerene
FePt nanosphere
SnO2 nanoflower Silver nanocubes Titanium nanoflower

8. Methods for creating nanostructures
Mechanical grinding
Wet Chemical Synthesis of Nanomaterials
Sol-gel process
Gas Phase synthesis of nanomaterials
Sputtered Plasma Processing
Particle precipitation aided CVD
Laser ablation

9. Nanostructured material performance in
corrosive environments
Corrosion – definition
Transformation of a metal in a metallic ion through its
interaction with the species in the exposed environment.

10. Corrosion process continuity....
No interaction
No corrosion
Immunity
Active metal
Metal with
corrosion product
layer
Very rare
Metal or alloy cannot
be used in the
considered
environment
Good performance or
localized corrosion

11. The four practices of corrosion
protection
•select another metal or alloy or modify the composition or
the microstructure of the metal or alloy: materials science
• interpose a barrier between the metal and the environment:
metallic and organic (paint) coatings
• condition the environment: by adding corrosion inhibitors or
oxygen scavengers or by deairating
• cathodic or anodic protection: by modifying the potential
differences across the metal and the environment

12. Nanocrystalline (nc) x microcrystalline
(mc)
Nanocrystalline (nc) x microcrystalline (mc)
• The use of nc materials is being developed for different
purposes, especially due to the physical and mechanical
properties such as wear resistance, smoothness and brightness.
• nc materials present a higher density of “microstructural flaws”:
the intercrystalline (intergranular) “paths” increase up to almost
50 % when the grain size decreases from 1 μm to 5 nm.
• The classical principle states that the intergranular paths present
a higher energy than the bulk grain due to the presence of
voids, impurities, segregations. Thus, chemical reactions and
diffusing processes are enhanced within grain boundaries.

13. Nanocrystalline nickel nc ultrapure Ni is produced by
:
electrodeposition
This material is preferred when better physical and mechanical properties are
required:
How about the corrosion resistance?
Studies in H2SO4
[
• Nanocrystalline (nc) electrodeposited - 32 nm;
• Microcrystalline (mc) 90 % cold rolled and full annealed – 100 μm
MISHRA, R.; BALASUBRAMANIAN, R. Effect of nanocrystalline grain size on the electrochemical and corrosion behavior of nickel.
Corrosion Science, 46 (2004, 3019- 3029)
ROFAGHA, R. et al; The corrosion behavior of nanocrystalline nickel. Scripta Mettallurgica et Marterialia, 25 (1991) 2867-2872

14. After electrochemical tests

15. In classical theory, the performance of Ni in
diluted H2SO4 depends on the characteristics
of the passive film. The film breakdown occurs
within intergranular paths.
Thus, the increase of intergranular paths of the
nc Ni increases the corrosion susceptibility
of nc Ni in comparison to the mc Ni.
nc presents better physical and mechanical
properties, but is more prone to
corrosion.

17. Fe8Al nanocrystalline alloy
Results:
• pH = 1: greater corrosion of the nc alloy was observed.
Classical behavior was observed: the corrosion was
more intense in nc alloy
due to its higher intergranular paths.
• pH = 6: less corrosion of the nc alloy was observed.
Once again the classical behavior was observed: at this
pH, a passive film of aluminum oxide was formed. The
film formed on nc alloy was more effective than the
film formed on mc alloy
This later behavior can be explained as follows…

19. High temperature oxidation (> 650 oC)
nc alloy coating – nc thin films
• High temperature resistant alloys normally contain Ni, Cr and Al . The oxidation
resistance of these alloys depends mainly on the formation and preservation of an
oxide layer constituted mainly by Cr2O3 and/or Al2O3. Large amount of Cr and Al
are required. Al impairs the mechanical properties of these alloys.
• The formation and preservation of the oxide film is diffusion dependent (as
previously mentioned)
• nc high temperature resistant alloys: the amount of Al required is lower in nc
alloy because the rate of Al diffusion is enhanced due to high density of grain
boundaries. This behavior permits a formation of more uniform, adherent and
compact oxide layer. For example: in Ni-Cr mc alloys, 8 % of Al is required
whereas in Ni-Cr nc ,only 2 % of Al guarantees a good performance

21. The four practices of corrosion
protection
• select another metal or alloy or modify the
composition or the microstructure of the metal or
alloy: materials sciene
• interpose a barrier between the metal and the
environment: metallic and organic (paint) coatings;
• condition the environment: by adding corrosion
inhibitors or oxygen scavengers or by deairating;
• cathodic or anodic protection: by modifying the
potential differences between the metal and the
environment

22. Ceramic nanoparticles
Nanoparticles of TiO2, SiC, Al2O3 (pigments)
are incorporated into organic coatings in
order to enhance the barrier properties
and, thus, to improve the corrosion
resistance.

23. There is a significant improvement of the paint performance: better
corrosion resistance, gloss retention, better resistance to mechanical
damages (the nanoparticles are hard)!

24. Ceramic nanoparticles incorporation in
sol-gel films
Thin films with ceramic-TiO2 nanoparticles applied on AISI 316 stainless
steel – the protection mechanism is different in dark and light
conditions:
• In the absence of light: the TiO2 coating acts as an effective barrier.
Experiences show that, in a dark condition, 40-nm of TiO2 nanoparticles,
incorporated in a 400-nm sol-gel film, are able to reduce the corrosion
current in three order of magnitude in chloride-containing solutions;
• In the presence of light: photoelectrons are generated in the conduction
bands of the TiO2 nanoparticles. These electrons are transferred to the
stainless steel substrate and cause a decrease of the open circuit
potential. In this situation, the stainless steel is subjected to cathodic
protection.

25. Conductive coatings
• It is possible to incorporate in the conductive
coatings organic or inorganic nanoparticles,
with oxidizing properties, such as MnO2,
V2O5, Fe2O3, Fe3O4.
• This practice guarantees the oxidizing capacity
(to shift open circuit potential to more
positive values) and thus, improve the
corrosion resistance capacity of the
conductive coatings.

26. • Tests were conducted :
– Conductive films obtained with polypirrol (elecodeposition using a rotating
electrode):
– Polypirrol+ Fe3O4 (particle size from 200 nm to 300 nm, clusters ~1 μm),

27. Nano-composite as Corrosion
Inhibitors
Nano-composite as Corrosion Inhibitors for
Steel Alloys
The application of nanotechnology in the
corrosion protection of metals has recently
gained momentum .A polymer Nano composite
coating can effectively combine the benefits of
organic polymers, such as elasticity and water
resistance, to that of advanced inorganic
materials, such as hardness and permeability

28. Environmental impact can also be improved by
utilizing nanostructure particulates in corrosion
inhibition, coating, and eliminating the
requirement of toxic solvents. Nano composites
have also proven to be an effective alternative
to phosphate-chromate pretreatment of
metallic substrate, which is hazardous due to
the presence of toxic hexavalent chromium

29. The present article reports some of the preliminary
investigations on the corrosion-resistance performance of
Nanocomposite. The corrosion-protective performance of Nano-
composite was evaluated in terms of physico-mechanical
properties, corrosion rate, and SEM studies . In the last two
decades, nanotechnology has been playing an increasing
important role in supporting innovative technological advances
to manage the corrosion of steel. Significant advancements have
been made to improve the management of steel corrosion
through research, development, and implementation; and
nanotechnology has been playing an increasing important role in
supporting innovative technological advances.

30. First of all, improved understanding of corrosion and inhibition mechanisms
has been continually achieved through characterization and modeling of the
steel surface and corrosion products at various length scales down to the
nanometer scale
Secondly, nanotechnology has been employed to enhance the inherent
corrosion resistance and performance of the steel itself, by achieving the
desirable finely crystalline microstructure of steel (e.g., Nano-crystallization)
or by modifying its chemical composition at the nanometer scale (e.g.,
formation of copper nanoparticles at the steel grain boundaries). Metallurgy
approaches to the production of high-performance steel with a fine-grain
structure and/or self-organization of strengthening Nano phases (carbides,
nitrides, carbonitrides, intermetallides) have been burgeoning under the
guide of Nano technological principles, including Nano processes for steel
melting and micro alloying, mechanical pressure treatment (e.g., intense
plastic deformation), and heat treatment (e.g., superfast quenching of melts)
. One such technology commercialized in the U.S. produces high-performance
carbon steels that feature a “three-phase microstructure consisting of grains
of ferrite fused with grains that contain dislocated lath structures in which
laths of martensite alternate with thin films of austenite” .

31. Thirdly, nanotechnology has been employed to reduce
the impact of corrosive environments through the
alternation
of the steel/electrolyte interface (e.g., formation of Nano-composite thin film
coatings on steel). Significant improvements in the corrosion protection of
steel have been reported through the co-deposition of Ni-SiC or Ni-Al2O3
Nano composite coatings on mild steel and the application of TiO2-
naoparticle sol-gel coatings or multilayer polyelectrolyte Nano films on 316L
stainless steel The incorporation of Nano-sized particles (e.g., polyaniline/
ferrite, ZnO, Fe2O3, hallo site clay, and other nanoparticles) into conventional
polymer coatings also significantly enhanced the anti-corrosive performance
of such coatings on steel substrates .Recent progress in the use of
nanomaterial’s for corrosion control is summarized in a 2007 review article
,which discussed the incorporation of nanoparticles in ceramic coatings,
polymer coatings, and hybrid sol-gel systems, for improved properties (e.g.,
resistance to corrosion and high-temperature oxidation, self-cleaning, and
anti-fouling).

32. Polymer –Clay Nano composite materials as corrosion
inhibitors for steel: A series of polymer-Clay Nano
composite materials that consisted of emeraldine base of poly(O-
ethoxyaniline) and layered montmorillonite clay were prepared and tested as
corrosion inhibitors for steel in acidic, alkaline, and NaCl aqueous electrolytes,
polyclay nanocomposite at low clay loading up to 3wt.% in the form of coating
on steel, were found to exhibit much superior corrosion inhibition effect as
compared to poly(o-ethoxyaniline) itself. The polymer-clay nano materials
were evaluated in 5% (wt %) aqueous NaCl electrolyte, by electrochemical
measurements. Corrosion potential, polarization resistance, corrosion
current, and impedance spectroscopy show that the increasing Clay loading
up to 3% enhance corrosion inhibition efficiency. The corrosion inhibition
efficiency increases in case of polymer-Clay Nano composite and its greater
than using polymer without clay, so its preferred to use poly-clay Nano
composite than polymer itself to enhance the corrosion inhibition efficiency
of steel in aqueous corrosive media . Sulfonated polyurethanes (SPU) were
.
used as corrosion inhibitor for mild steel in acidic solution

33. The sulfonation of the >N-H groups of the urethane linkages was
confirmed from Nuclear Magnetic Resonance (NMR) and Fourier
Transform Infra Red (FTIR) spectroscopic techniques. The inhibition
efficiency of sulfonated polyurethanes, prepared from two different
routes, was investigated using different techniques. The effects of
microstructure of polyurethane (PU), degree of sulfonation, time of
immersion and temperature on the inhibition of corrosion were
discussed. The disc-like nanoparticles, so-called nanoclay, either
suspended or chemically attached to SPU chains (nanocomposites)
dramatically enhanced the inhibition efficiency for mild steel in acidic
medium. All the inhibitors retard the corrosion rate by getting themselves
adsorbed on the corroding surface by following the Langmuir adsorption
isotherm. The surface analysis of inhibited and uninhibited samples was
performed using Scanning Electron Microscopy (SEM) and Atomic Force
Microscopy (AFM). Among the various inhibitors used, the nanocomposite
of polyurethane was the most effective. Molecular modeling helped in
determining the extent of packing of the SPU chains leading to better
inhibition efficiency.

34. Nano- coating
Self-cleaning paints and biocidal coatings
There is a great interest in the design and development of surfaces
that not only provide biocidal activity but are also easy to clean and
even self-cleaning. Most of such coatings acquire their biocidal/self-
cleaning capacity by incorporating specific nanoparticles: basically
silver (Ag) and titanium oxide (TiO2). Nano TiO2 is used for
developing anti-UV, anti-bacterial and self-cleaning paints. This
possesses self-cleaning hydrophobic properties, which causes water
droplets to bead-off of a fully cured surface picking up dirt and
other surface contaminants along the way. This self-cleaning action
helps clean and maintain important surfaces and to accelerate
drying, leaving the surface with minimal spotting. A recent study by
Cai et al. utilizes corona treatment technique, inert sol–gel coating
and anatase TiO2 layer. With the corona treatment, an organic
surface was activated to allow a uniform TiO2 sol–gel coating.
Nanoparticles of surface treated Al2O3 molecules help increase
hydrophobicity and increase scratch resistance.

35. Microbial evolution on a wide variety of surfaces can cause
corrosion, dirt, bad adour and even serious hygiene and health
problems. (Advanced Nanostructured Surfaces for the Control of
Biofouling), a European Union research project38 is investigating
how to prevent the build-up of organisms on surfaces under
marine conditions to avoid biofouling. The project aims to use
nanostructuring to significantly reduce the adhesion of
organisms to surface in aquatic environments, and thus control
the foul in process without the use of toxic biocides such as
copper and organotin compounds that prevent fouling by killing
organisms. Nanostructuring of the surface alters the wetting
properties and is intended to signal that the site is not suitable
for the organisms to settle.