This document describes a study comparing the mechanical and microstructure properties of thermal spray TiO2 coatings on an aluminum alloy to hard chromium plating. The objectives are to apply TiO2 coatings via thermal spraying and compare to hard chrome plating. Testing shows the thermal spray coatings have higher hardness, better wear resistance, and could be a more environmentally friendly alternative to hard chrome plating which uses toxic hexavalent chromium.

2. PROJECT ABSTRACT
 Automotive manufacturers have specified chromium plating for decades
because of its appearance, wear and corrosion resistance.
 Chromium plating affect human health and environment badly because
of the use of toxic substances in the plating process.
 The present study describes and compares the mechanical and
microstructure properties of Thermal Spray coating over Chromium plating
on a Aluminium alloy.
 The objective of the present work is to apply the TiO2 coatings thermally
over Aluminium alloy 6063 and compare with chromium plating.
 It was found that the Thermal spray coating, presented the best wear
resistance and higher hardness values over chrome plating.
 The Fine Thermal spray coatings will demonstrate superior performance
than hard chrome and they can be proposed as an alternative to hard
chrome platings.

3. INTRODUCTION
 Thermal spraying also commonly known as Metal spraying, is a coating
process in which melted or heated materials are sprayed onto the surface
of another material.
 Oxygen and fuel is fed along with a coating material (TiO2) in a powder
form. A heat source which literally melts the powder into tiny droplets and
sprayed onto surfaces at supersonic velocity (upto 1200m/s).
 This high kinetic energy of hot powder particles on impact with surface
build up a very dense and strong coating.
 Thermal sprayed coatings uniquely enhance and improve the performance
of the component.
 Thermal sprayed coatings can be an effective alternative to several surface
treatments including Nickel and Chrome Plating, heat treat processes,
anodizing, and weld overlay.

4. REASONS TO AVOID CHROME PLATING
PROCESS IN VEHICLES
 Functional hard chrome plating is a critical process associated with complex
manufacturing and maintenance operations.
 The chrome plating bath contains toxic substances, hexa-valent
chromium(Cr+6) & chromium trioxide(CrO3), which has many adverse
health and environmental effects.
 The Environmental Protection Agency(EPA) of U.S. list hexavalent
chromium as a hazardous air pollutant.
 The European Parliament (21/10/2000) in the Official Journal of the
European Union Directive 2000/53/EC, strictly prohibits the use of lead,
cadmium, hexa-valent chromium and mercury in all vehicles.
 The total permissible amount of hexa-valent chromium is limited to 2 gram
per vehicle. This directive must be implemented as National law in the
Member States of the European Union.

5. LITERATURE SURVEY
Bruce D. Sartwell, under the Naval Research Laboratory,
experimented the replacement for Hard Chrome Plating in
manufacturing and maintenance operations on Military and
Commercial Aircraft.
Dale M. Homeniuk, expertise in the field of Coatings and
Hydraulics experimented on Thermal Spray Coatings in Pressure
Vessels, Recovery Boilers, Heat Exchanger Tube Sheets and Pressure
Piping.
J.A. Picas, A. Forn and G. Matthaus experimented on Thermal
Spray Coating of CrC-NiCr as an alternative to hard chrome for
pistons and valves.

6. SCOPE AND OBJECTIVES
 The present study describes and compares the mechanical and
microstructural properties of Thermal Spray coating over Chromium plating
on a Aluminium alloy.
 The objective of the present work is to apply the TiO2 coatings thermally
over Aluminium alloy 6063 and to do a comparative study with Hard
Chrome Plating.
 During spraying, the hot melted material show a higher decomposition and
spread evenly over the surface, thus produce coatings with high hardness.
 The reason why Thermal Spray Coating for engine application is preferred
is because of its low porosity (<1%), rough adherent coatings (bond
strength>50 MPa) which have an oxide content less than 1% even for
reactive metals.
 The Fine Thermal spray coatings will demonstrate superior performance
than hard chrome and they can be proposed as an alternative to hard
chrome plating.

7. MATERIALS REQUIRED

8. EXPERIMENTAL WORK
.
Thermal Spray Coating Hard Chrome Plating
on
Aluminium Alloy 6063 (Base Metal)

9.  Microstructure Examination
• Electron Microscopy (Scanning Electron Microscope)
 Micro Hardness Test
 Wear Resistance Test
 Coating Measurements

10. Microstructure Examination Using
Scanning Electron Microscope (SEM)
.
Microstructure of TiO2 Thermal Spray Coated Al alloy
Microstructure of Hard Chrome Plated Al alloy

11. Micro Hardness Test
 The Vickers hardness test method is mostly used for small parts,
thin sections, or case depth work.
 A range of light loads using a diamond indenter to make an
indentation which is measured and converted to a hardness value
 The microhardness test was conducted on three different places on
both test samples with an applied load.
 The result shows that the hardness values for thermally sprayed TiO2
coated Al alloy are much higher than hard chrome plated Al alloy.
Sample Piece Vickers Hardness Number (HV) Average
Chrome Plated 632 618 640 630
TiO2 Coated 974 927 935 945

12. Wear Resistance Test
 Wear measurement is carried out to determine the amount of
materials removed (or worn away) after a wear test.
 The weight of the samples are carefully measured before and after
a wear test. The difference in weight before and after test
represents the weight loss caused by wear.
 From the Wear test results, it is clearly seen that abrasion loss of
hard chrome plated Al alloy is more than TiO2 coated Al alloy.
 This shows that the thermally sprayed TiO2 coated Al alloy has
more wear resistance.
Sample
Piece
Initial
Weight (g)
Final
Weight (g)
Abrasion
Loss (g)
Percentage
Loss %
Chrome Plated 1.8942 1.7680 0.1262 6.66
TiO2 Coated 1.7629 1.6856 .0773 4.38

13. Thermal Spray Coating
Advantages
Less capital cost compared to Chrome Plating.
Requires less floor space.
Increased Wear Resistance & Service Life.
Wastes from thermal spraying are not toxic.
Easy disposal of waste particles.
Improved Corrosion Resistance.
Better Bonding Characteristics.
Bonds to a Wider Range of Materials.
Higher Hardness.
Thick Coating Capability.

14. CONCLUSION
 Thermal Spraying is not about to completely replace Chrome Plating
the world over. However, it will offer an alternative solution to
Chrome Plating.
 Various industry sectors are moving forward with thermal spraying
in areas where chrome plating was trusted for many years.
 In developed countries, the use of chrome plating has already
been banned due to its undesirable effects of its effluents to
environment and ecological system.
 For future successful applications of TiO2 Thermal spray coatings
as an alternative to chrome Plating, many factors like heat
resistance, friction coefficient, costs, environmental and health
issues have to be considered collectively.