Synthesis and Characterization of a New Titanium Alkoxide
Used in Anticorrosive Protection
FLORENTINA MANDEA1, IOANA JITARU2, OVIDIU OPREA2, LAURA ALEXANDRESCU2
SC Anticorosiv SA, 57 Th. Pallady Blv., 032258, Bucharest, Romania
2
Politehnica University of Bucharest, Faculty of Applied Chemistry and Science of Materials, 1 Polizu Str., 011061, Bucharest,
Romania
1
This paper deals with synthesis and comprehensive characterization of a new titanium alkoxide obtained in
Ti(IV)-isopropyl alcohol-pinacol system. The formulation as [Ti5(pin)5(OiPr)10] cluster was based on elemental
analysis, FT-IR spectra, mass spectrometry and thermal analysis.The use of titanium alkoxide in anticorrosion
coating paints is also tested. The coating characteristics were evaluated from chemical resistance tests as
well as salt spray tests. Coatings morphology was analyzed by atomic force microscopy.
Keywords: titanium alkoxide, metal-complex cluster, mass spectrometry, corrosion protection
Incorporation of corrosion inhibitors into coatings films
can improve their protective ability, suppressing the
corrosion process in the defects. Phosphates, vanadates,
borates, titanium, cerium and molybdenum compounds
were found to have inhibiting action on the corrosion
processes [1-3].
Titanium alkoxides are important ingredients for
application in organic coating industry. They have a very
high reactivity determined by the different polarizability of
the metal and organic groups.
Titanium alkoxides are crosslinking agents which
control paints and dyes viscosity [4]. They are used in the
hardening of polybutadiene resins hardening during zinc
plate coating in food industry and in the obtaining of
butadiene-styrene copolymer based flexible dye. Titanium
alkoxides also increase the corrosion resistance of
polystyrene dyes on metallic surface and polypropylene
dyes used for metallic wires insulation [5-9].
Titanium alkoxides are also used for the crosslinking of
polysiloxanes and the preparation of dyes with high
adherence, waterproof, heat and abrasion resistance. The
use of titanium alkoxides increases flexibility, elasticity,
chemical agents, electrical and mechanical resistance as
well as thermal stability of air-drying dyes based on polyvinyl
alcohol [10-15].
The gelation capacity of titanium alkoxides can explain
the adherence at the surfaces of paints, dyes, inks and of
other materials [16].
Experimental part
Synthesis of [Ti5(pin)5 (OiPr)10] alkoxide
The synthesis has been carried out in different
experimentally conditions by variation of some parameters
like:
- nature of Ti(IV) salt (TiCl4 or Ti(OiPr)4)
- (Ti(IV): pinH2 molar ratio
- temperature, atmosphere and time of reaction.
A reproducible, pure Ti alkoxide with the formula
[Ti5(pin)5(OiPr)10] has been obtained in argon atmosphere
by mixing isopropyl alcohol (HOiPr) solutions of titanium
(IV) isopropoxide (Ti(O i Pr) 4) and 2,3 dimethyl-2,3butanediol or pinacol (pinH2) in Ti(IV): pinH2 = 1:1 molar
ratio at room temperature. After 30 min of magnetical
stirring, a white precipitate appeared which have been
filtered out, washed with ether and stored under inert
atmosphere.
Anal. Found: Ti% 16.25; C% 47.8; O% 48.7.
Calc. Ti% 17.14; C% 48.2.; O% 49.5
Synthesis of protective coating based on titanium alkoxide
Samples of galvanized steel 10 x 15 x 1.3 from System
Invest, Arad have been used.
98 g of additivated ortoftalic resin was mixed with 2 g of
titanium alkoxide by magnetic stirring at 800-1000 rot/min.
When the mixture became homogenous 2 g of methyl
ethyl ketone peroxide was added. This composition was
deposited by pulverization on the galvanized steel surface,
drying for 48 h at 230C and analyzed using atomic force
microscopy (AFM).
FT-IR spectra have been recorded with a Perkin-Elmer
spectrophotometer using KBr pellets as reference in the
4000-400 cm-1 range.
X-ray diffraction pattern have been registered on a
Bruker-AXS type D8 ADVANCE difractometer.
Mass spectra have been recorded on GCQ
THERMOELECTRON apparatus
AFM data CP II Scanning Probe Microscope,
Transmission Electron Microscope, Veeco Instruments –
Germany 2005, with resolution of 0.1 nm XY and 0.007 nm
Z, 3D visualization; samples have been analyzed in 0 -20
mm section.
Corrosion studies have been performed in a saline mist
room Angelantoni Industrie SpA, DCTC-F00231 model, Italy.
All chemicals have been used as received without
further purification.
Results and discussions
Characterization of [Ti5(pin)5 (OiPr)10] alkoxide
The FT-IR spectra of titanium(IV) isopropoxide, pinacol
and [Ti5(pin)5(OiPr)10] alkoxide have been recorded to
confirm our suppositions regarding the coordination mode
of the ligands, the experimental data being assigned
according to the literature (fig. 1).
The FT-IR spectrum of the synthesized alkoxide showed
characteristic bands positions and intensities which can
be assigned both to pinacol and isopropyl alcohol.
In table 1 the main characteristic bands and their
assignment are presented.
All characteristic Ti-O, Ti-O-Ti, Ti-O-C bonding bands are
present in the infrared spectrum of the synthesized
compound like in the case of other alkoxides.
The absence of ν(OH) frequency in the spectrum of the
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Fig. 2. Thermodifferential analysis of [Ti5(pin)5(OiPr)10] alkoxide
Fig. 1. FT-IR spectra of: a. titanium(IV) isopropoxide;
b. synthesized [Ti5(pin)5(OiPr)10] alkoxide;
c. pinacol in the 4000-400 cm-1 range
calculated one for [Ti5(pin)5(O iPr)10] cluster proposed
formula is 28.3%. The formation of TiO2 after 400- 4500C
occurred and its identification was made by X-ray
diffractometry (fig. 3).
Table 1
THE MAIN INFRARED CHARACTERISTIC BANDS AND THEIR ASSIGNMENT
synthesized alkoxide is a proof of the deprotonation of the
OH group on pinacol binding with the metal.
The thermal behavior of the synthesized
[Ti5(pin)5(OiPr)10] alkoxide has been also studied using
thermodifferential analysis.(fig. 2).
The oxidative decomposition of the synthesized alkoxide
begins around 1200C and ends at 450-5000C with three
peaks in the DTA curve: the first and the second
endothermic and the third exothermic. The first two
endothermic peaks at 150 and 2300C respectively can be
correlated to the partial loss of pinacol or isopropyl alcohol
and the third exothermic peak at 3800C can be assigned to
the total burning of organic molecules.
The total experimentally mass loss is 27.5% and the
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Fig. 3. X-ray diffractogram of the final product obtained by
[Ti5(pin)5(OiPr)10] cluster calcination for 1 h at 5000C.
573
The mass spectrum of the synthesized [Ti5(pin)5(OiPr)10]
alkoxide has been recorded (fig. 4) and the molecular peak
MH+ is present at 1409 m/z.
Fig. 5. Proposed structure for [Ti5(pin)5(OiPr)10] cluster
Fig. 4. Mass spectrum of [Ti5(pin)5(OiPr)10] cluster in isopropyl
alcohol/toluene (6/1) solution recorded at 10V in 200-1500 m/z
range
The other peaks in the mass spectrum can be assigned
to different fragments obtained by a partial breaking of the
initial molecule, so:
-1296 m/z corresponds to fragment [Ti5(pin)3(OiPr)14];
- 778 m/z corresponds to fragment [Ti4(pin)3(OiPr)9];
- 787 m/z corresponds to fragment [Ti3(pin)3(OiPr)5]+;
- 448 m/z corresponds to fragment [Ti2(pin)(OiPr)4]2+;
- 284 m/z corresponds to fragment Ti(OiPr)4.
Characteristic peaks for isopropyl alcohol molecule
breaking such as methyl ethyl ether or for alkoxide
hydrolysis with m/z less than 200 can not be visualized in
this spectrum.
Based on physico-chemical characterization, theoretical
calculation and by comparison to other titanium alkoxide
clusters containing ethylene glycol a structure with
coordination numbers 5, 6 and 7 and μ3 η2, μ2 η2, μ4 η2
environment was proposed for the synthesized
[Ti5(pin)5(OiPr)10] alkoxide (fig. 5).
Characterization of protective coating based on titanium
alkoxide
The AFM technique was used in order to assess porosity
and structure of the protective coating (polyvinyl type)
containing titanium alkoxide by comparison to the
protective coating without titanium alkoxide.
In table 2 comparative AFM data for protective coating
containing titanium alkoxide and without titanium alkoxide
are presented.
Table 2
AFM PARAMETERS FOR PROTECTIVE
COATING CONTAINING TITANIUM ALKOXIDE
AND WITHOUT TITANIUM ALKOXIDE
Fig. 6a. AFM images for
protective coating with titanium
alkoxide
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Fig. 6b. AFM images for protective coating without titanium alkoxide
Fig.7. Histogram indicating the chemical corrosion resistance of
polyvinyl coating additivated with titanium alkoxide after 6 months
Fig.8. Histogram indicating the salt sprays corrosion resistance of
polyvinyl coating additivated with titanium alkoxide after 2000 h
Important differences between protective coating
without titanium alkoxide and with titanium alkoxide can
be observed from AFM data. The significant smaller values
of surface area and specific volume for the sample
containing titanium alkoxide are correlated to a more
compact structure of the coating without pores and microfissures, which makes this titanium alkoxide containing
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coating suitable for industrial applications. The presence
of pores and micro-fissures leads to coating degradation
in time along with coating detaching from the surface.
The smaller surface area is correlated to the smaller
smoothness of the surface and the better resistance to
water vapors, chemicals and salt spray tests.
575
Corrosion resistance tests of vinyl-ester coating additivated
with [Ti5 (pinacolate)5 (OiPr)10] alkoxide
Chemical resistance (in acidic, basic or organic
medium) as well as salt sprays resistance of titanium
alkoxide additivated coatings in comparison with those
without titanium additive has been tested. The variation of
the % mass loss of coating in different chemical corrosive
agents after six months is observed in figure 7.
The tests have indicated the increasing corrosion
resistance of polyvinyl coatings in HNO3, H2SO4, KOH, NH3
or xylene by additivation with the studied titanium alkoxide.
The results of neutral salt spray tests are presented in
figure 8. The corrosion resistance of titanium additivated
coating was double than that without additivation.
Conclusions
A new titanium alkoxide has been synthesized and
characterized by elemental analysis, FT-IR and mass
spectrometry, thermodifferential analysis and X-ray
diffractometry. A cluster type structural formula has been
proposed for [Ti5(pin)5(OiPr)10]. The compound is stable up
to 400-450 0C when it transforms in TiO 2. Important
differences between protective coating without titanium
alkoxide and with additive titanium alkoxide can be
observed from AFM data. The tests of chemical corrosion
resistance of polyvinyl coatings additivated with the
titanium alkoxide studied indicated the increasing of
anticorrosive property of the coatings.
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Manuscript received: 31.03.2008
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