FIELD OF THE INVENTION
The present invention relates to a method for determining aluminium content in
aluminium paints.
BACKGROUND OF THE INVENTION
Aluminium paints are used extensively as coating material on structural for prevention of
corrosion. Aluminium content in the paint is very important for the quality of the paint.
Deterioration in the life of painted surfaces can be correlated with the aluminium content
in paints.
There is no existing method for chemical analysis of aluminium content in paints. A need
therefore, exists for the estimation of aluminium content in paints.
SUMMARY OF THE INVENTION
The main object of the present invention therefore is to provide a method for estimating
the aluminium content in paints used for providing a protective coating on structural
surfaces against corrosion. The process for such testing of aluminium content in paints
will broadly involve steps like collection of samples, removal of any organic portion of
the paint from the sample, bringing the residue into an aqueous solution, measuring the
aluminium content of the solution by inductively coupled plasma technique and checking
for repeatability and reproducibility of the method.
Thus, the present invention provides a method for determining aluminium content in
aluminium paints comprising the steps of
a) heating a paint sample on a hot plate for removal of the organic contents;
b) adding gradually 10% NaOH solution in hot condition until reaction with the
sample ceases;
c) cooling the material to room temperature and adding cold H2O2 solution for
complete oxidation;
d) adding concentrated hydrochloric acid and boiling to bring the entire residual
mass into a solution;
e) filtering the mass by filter paper and collecting the filtrate in a volumetric flask;
f) washing the residue with hot water to make it acid free;
g) igniting the residue with the filter paper at a temperature of 1000°C;
h) fusing the ignited material with potassium pyro sulphate, dissolving the fused
mass in dilute hydrochloric acid and transferring the mother solution to a
volumetric flask;
i) adding 2 gms of sodium carbonate, 1 gm of borax, 20 ml concentrated HNO3, 20
ml of solution of step (h) and 5 ml of 2000 ppm copper solution in a 250 ml
volumetric flask;
j) making up the volume upto the mark while shaking well; and
k) calibrating a program on an ICP spectrometer and measuring the aluminium
content.
DETAILED DESCRIPTION OF THE INVENTION
For estimation of aluminium in paints, a sample of the paint of say 0.5 gms can be taken
in a beaker. The beaker can be made to a material like for example, Teflon and heated on
a hot plate so that the organic constituents of the paint like base oil and thinner can be
removed. The material can be heated upto a temperature of 200°C for about two hours.
10% sodium hydroxide NaOH (aqueous solution wt./vol) is then added slowly to the
material in heated condition till the reaction ceases. The Teflon beaker can then be
removed from the hot plate and allowed to be brought to room temperature.
Cooled hydrogen peroxide H2O2 solution is then added by drops for complete oxidation
of the material.
10-15 ml of concentrated hydrochloric acid HC1 is then added and boiled a little to bring
the entire residual mass into a solution.
The solution is then filtered, which can be done by using double Whatman 41 filter paper.
The filtrate can be collected in a
volumetric flask of say 100 ml capacity. The residue is then
washed with hot water to make it acid free.
The washed residue is then taken into a platinum crucible along
with the filter paper,dried and ignited at a temperature of 1000°
C. This can be done in a muffle furnace. The ignited material is
then fused with a minimum quantity of potassium pyro sulphate.
The fused mass is dissolved in a minimum quantity of dilute
hydrochloric acid and transferred to the mother solution in the
volumetric flask.
The volume is made up to the mark with distilled water. 2 gms of
sodium carbonate, 1 gm of borax, 20 ml of concentrated nitric
acid, 20 ml of solution from the previous step and 500 ml of 2000
ppm copper solution are taken in a 250 volumetric flask. The
volume is made up to the mark and shaken well. A calibration
program of an ICP spectrometer is then made using synthetic
aqueous standards covering a range of concentrates of aluminium
upto 50%.
The ICP spectrometer used for the purpose can be of Spectro
Analytical, Germany. The ICP's spectrometer is used for measuring
the aluminium content.
Repeatability tests can be carried out.
From a particular sample,the following values were obtained
6.74, 6.51, 6.67, 6.81, 6.58, 6.65, 6.52, 6.75 and 6.69 % which
provide an average value of 6.65X with a standard deviation of
0.10%.
WE CLAIM
1. A method for determining aluminium content in aluminium paints in a sample
comprising the steps of:
(a) a paint sample of 5-10 gm is heated at 200°C for three hours on a hot plate
for removal of organic components;
(b) adding gradually 20-30 ml of 10% NaOH aqueous solution in wt/vol in hot
condition until reaction with the sample ceases;
(c) cooling the material to room temperature and adding cold H2O2 solution 3-4 ml
for complete oxidation;
(d) adding 10-15 ml of concentrated hydrochloric acid and boiling to bring the entire
residual mass into a solution;
(e) filtering the mass by double Whatsman 41 filter paper and collecting the filtrate in
a volumetric flask, of 100 ml capacity;
(f) washing the residue with hot water to make it acid free;
(g) igniting the residue with the filter paper in a platinum crucible inside a muffle
furnace at a temperature of 1000-1050°C;
(h) fusing the ignited material with 2-4 gms potassium pyro sulphate dissolving the
fused mass in 10-20 ml dilute hydrochloric acid and transferring the molten
solution to a volumetric flask;
(i) adding 2-4 gms of sodium carbonate, 1 -2 gm of borax, 20 ml concentrated Nitric
acid to 20 ml of solution of step(h) and adding 500-600 ml of 2000 ppm copper
solution in a 250 ml volumetric flask;
(j) making up the volume up to the mark while shaking well and
(k) calibrating a program on an ICP spectrometer for measuring the aluminium
content using synthetic aqueous standards covering a range of concentrates of
aluminium.
characterised in that said sample in the form of solution is aspirated into argon plasma
wherein the different constituents of the sample get excited to higher energy levels
and while coming back to the ground state, they emit characteristic radiation and
intensity of the characteristic radiation of the element of interest is measured using
photo multipliers or CCD detectors and by referring to the calibration graph stored in
the system, concentration of aluminium is known (Aluminium characteristic wave
length monitored is 308.215 nra).
2. The method as claimed in claim 1, wherein different values can be obtained by
repeating steps (a) to (k) for a given sample.
3. The method as claimed in claim 1, wherein ICP spectrometer used is of spectro
analytical, Germany.

The invention discloses a method for determining aluminium content
in aluminium paints method for determining aluminium content in
aluminium paints. The method comprising the steps of heating a
paint sample on a hot plate for removal of the organic contents;
adding gradually 10% NaOH solution in hot condition until reaction
with the sample ceases; cooling the material to room temperature
and adding cold H2O2 solution for complete oxidation; adding
concentrated hydrochloric acid and boiling to bring the entire residual
mass into a solution; filtering the mass by filter paper and collecting
the filtrate in a volumetric flask; washing the residue with hot water
to make it acid free; igniting the residue with the filter paper at a
temperature of 1000°C; fusing the ignited material with potassium
pyro sulphate, dissolving the fused mass in dilute hydrochloric acid
and transferring the mother solution to a volumetric flask; adding 2
gms of sodium carbonate, 1 gm of borax, 20 ml concentrated HNO3,
20 ml of solution and 5ml of 2000 ppm copper solution in a 250 ml
volumetric flask; making up the volume upto the mark while shaking
well ; and calibrating a program on an ICP spectrometer for
measuring the aluminium content.