TITLE:
A process for producing a functionalized graphene used for protecting the
metals from corrosion.
FIELD OF THE INVENTION:
The present invention relates to a process for producing a functionalized
graphene used for protecting the metals from corrosion.
BACKGROUND OF THE INVENTION:
Graphene is a two-dimensional (2D) crystal of carbon atoms arranged into
a honeycomb lattice. Graphene is a basic building block for graphitic
materials of all other dimensionalities. It can be wrapped up into OD
fullerenes, rolled into 1D nanotubes or stacked into 3D graphite. Graphene
has been at forefront of research from past several years because of its
spectacular physics [1] and application potential arising from its unusual
mechanical, thermal, optical, chemical, and electrical properties. Graphene
is potential material for hydrogen storage because of its unique property to
adsorb hydrogen [2, 3]. We have exploited this property of graphene in
using it as a corrosion inhibitor for metals.
Corrosion inhibitor acts as retarding catalyst, when added in small
concentration to a corrosive environment. Various types of inhibitors have
been developed through empirical experimentations. Sodium chromate
acts as a corrosion inhibitor for aluminium metal in acidic environment [3-
5]. Benzyl thiocyanate prevents corrosion of cooper and brass in acidic

environment [6]. These inhibitor materials get adsorbed to metal surface
and suppress metal dissolution and reduction reactions. Arsenic and
antimony ions slow down the hydrogen-evolution reaction, consequently
effective in acidic environment [7]. Few inhibitor materials act as a
scavenger by remove corrosive reagents from the solutions. Sodium
sulphite and hydrazine removes dissolved oxygen from aqueous solutions.
OBJECTS OF THE INVENTION:
An object of this invention is to propose a process for producing a
functionalized graphene used for protecting the metals for corrosion.
Another object of this invention is to propose a functionalized graphene
which acts as an adsorption type corrosion inhibitor for steel or other
metals in corroding environment.
Further object of this invention is to propose a process for preparing a
functionalized graphene based corrosion inhibitor for improved corrosion
resistance of steel or metals with similar oxidation potentials.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 shows four different solutions of 1.4 M HCI with concentration of
FG varying from 0 mg, 1 mg, 10 mg and 100 mg.
Figure 2 shows four identical cold rolled steel sheet sample after being
cleaned with alkali solutions. Indices in the panel mention the FG
concentration of the solutions for which the samples are prepared.

Figure 3 shows four steel samples after being taken out from different
HCI/graphene solutions and dried. Indices in the panel mention the FG
concentration of the HCI solutions in which the samples were kept.
Figure 4 shows Tafel plot of four different steel samples. Tafel
measurements were performed on steel samples after 5 hours exposure to
different HCI / graphene solutions.
BRIEF DESCRIPTION OF THE INVENTION:
According to this invention a process for producing a functionalized
graphene used for protecting the metals from corrosion comprising
preparing graphite oxide by oxidative treatment pure graphite,
subjecting the graphite oxide to the step of exfoliation,
reducing exfoliated graphite oxide by using hydrazine hydrate to produce
graphene
washing the graphene thus obtained with water and methanol and
drying the graphene.
DETAILED DESCRIPTION OF THE INVENTION:
This invention describes about a technique for corrosion protection of
metals. In particular, we have developed a functionalized graphene based
corrosion inhibitor for improved corrosion resistance of steel or metals with
similar oxidation potentials. The functionalized graphene (FG) is a
corrosion inhibitor for steel in acidic environment.

Functionalized graphene samples were prepared using chemical methods.
In this method we first prepare graphite oxide (GO) by oxidative treatment
of highly pure graphite as described by Hummer Then, we exfoliate layers
of GO by ultrasonic treatment for 2-3 hours using an ultrasonicator (600-
1000 W, 20 kHz). Exfoliated GO consists of oxidized graphene sheets
having their basal planes decorated mostly with epoxide and hydroxyl
groups, in addition to carbonyl and carboxyl groups located presumably at
the edges. Functionalized graphene is obtained by partially reducing GO
using hydrazine hydrate, procedure explained later. Graphene obtained
through this process contains oxygen functionalities (C-O, C=O, O-C=O)
and nitrogen functionality (C-N), specified by C/O and C/N ratio roughly 5-
8 and 10-12 respectively.
Typically, pure graphene is hydrophobic in nature, so it cannot be
dispersed well in water. While, GO can be easily dispersed in water due to
presence of oxygen functionalities. In the foregoing procedure we do not
fully reduce GO so that a stable dispersion in water can be achieved. In
this method, GO (150 mg) was taken in a 500-mL round bottom flask and
water (150 mL) was then added, which gives a yellow-brown dispersion.
This dispersion was then sonicated using an ultrasonic probe (600 W, 20
kHz). Hydrazine hydrate (1.00 mL, 32.1 mmol) was then added and the
solution heated in an oil bath at 80° C for 24 hours. A cork having a
through hole of 5 mm diameter at the center was fitted at the neck of round
bottom flask. Functionalized graphene is obtained through vacuum
filtration and, washed with water and methanol, and dried on the funnel.
We also tried to fully reduce the GO by adding 5 ml hydrazine hydrate
(32.1 mmol) which gave a poor dispersion in water.

For testing corrosion inhibition behavior of FG, we have taken four identical
cold rolled steel sheets of size (30mmx50mm) and 13.5 g weight. We have
also prepared four solutions with different concentration of FG varying from
0, 1 mg, 10 mg and 100 mg in 220 ml of 1.4 M HCI. After adding FG all
solutions were stirred by magnetic stirrer for 10 minutes. Each solution with
volume 220 ml were taken in four different beakers as shown in Figure 1.
For doing the experiments, we have first cleaned steel samples with alkali
solution and then kept these samples for 5 hours inside four solutions of
1.4 M HCI with different concentration of functionalized graphene. Cleaned
steel samples are shown in figure 2.
We have removed the samples from solutions after keeping them for 5
hours in acidic environment with different concentration of FG and then
dried the samples with a dryer which gives hot air at temperature of 60° C.
Photographs of dried samples were taken as shown in Figure 3. From
these photographs, it is clear that steel samples which were kept inside
HCI solution with a concentration of 100 mg FG is less corroded. We have
also measured the weight of each sample after the experiment and
calculated weight loss as shown in Table 1. Weight loss data also confirms
the aforementioned results.
Here FG is acting as an adsorption-type inhibitor for steel in acidic
environment. Functionalized graphene flakes are flat monolayer of carbon
with very large surface area. When steel samples are kept in side acidic
solution with FG, due to presence of carbonyl and carboxylic functionalities
in FG these flakes get adsorbed by metal surface. Since graphene has a

tendency to adsorbs hydrogen. It slows down the hydrogen reduction
reaction and effectively reduces the hydrogen ion exchange current
density. Therefore, presence of graphene slows down the rate of
corrosion.
Moreover, further corrosion study is done by performing Tafel
measurements of four corroded and dried steel samples shown in Figure
3. These measurements were done using VersaStat by Princeton Applied
Research. Tafel plot for all the four samples is shown in Figure 4. From the
Tafel plots we have calculated the corrosion rate as shown in Table 2. We
have found that corrosion rate is lowest for sample which was kept in HCI
solution with highest concentration of FG. Since these measurements were
done after removing the steel samples from graphene solution, observed
slow corrosion rate for the sample kept in 100 mg graphene solution
confirms the adsorption of graphene on steel surface in the solution.


WE CLAIM:
1. A process for producing a functionalized graphene used for
protecting the metals from corrosion comprising
preparing graphite oxide by oxidative treatment pure graphite,
subjecting the graphite oxide to the step of exfoliation,
reducing exfoliated graphite oxide by using hydrazine hydrate to
produce graphene
washing the graphene thus obtained with water and methanol and
drying the graphene.
2. The process as claimed in claim 1 wherein the said step of exfoliated
is performed by using an ultrasonicator for 2-3 hrs.
3. The process as claimed in claim 1 wherein the said exfoliated
graphite oxide consists of oxidized graphene sheets having their
basal planes decorated mostly with epoxide and hydroxyI groups, in
addition to carbonyl and carboxyl groups located at the edges.
4. The process as claimed in claim 1, wherein the said step of
reduction is a partial reduction.
5. The process as claimed in claim 1, wherein the said functionalized
graphene contains oxygen functionalities and nitrogen functionality
specified as C/O and C/N in a ratio of 5:8 and 10:12 respectively.

ABSTRACT

A process for producing a functionalized graphene used for protecting the
metals from corrosion comprising preparing graphite oxide by oxidative
treatment pure graphite, subjecting the graphite oxide to the step of
exfoliation, reducing exfoliated graphite oxide by using hydrazine hydrate
to produce grapheme washing the graphene thus obtained with water and
methanol and drying the graphene.