Chapter 6 Recommendation and Future work

Chapter 6 Recommendation and Future work

Abstract

Aluminum is widely used in a plenty of industrial applications such as constructions, electrical engineering, transport and especially in aircraft industry for the manufacturing and production of different equipment and machineries. Despite the good properties of aluminum and its alloys, they are not perfect materials for engineering applications in all environments, since they suffer from corrosion caused by chemical interaction with their surroundings. Pitting corrosion is one of the major problems faced by aluminum components used in aircraft. In this project an experimental investigation is taken on the corrosion analysis of aluminum alloy material used in aircraft components. At present the nose landing gear undergoes severe corrosion problem and leads to failure of component. Pitting corrosion is localized accelerated dissolution of metal that occurs as a result of a breakdown of the protective passive film on the metal surface. This project provides a study about corrosion analysis of aluminum alloy (7076) used in aircraft components. Identification of material details, preparing test samples out of collected material and scope of improvements corrosion resistant recognized as key enabling to reduce the impact of corrosion on the integrity of critical aircraft assets. Hence three different types of coatings are developed and their corrosion resistance been tested.

In this project two types of heat treatment experiments been used to test the samples with coating condition and without coating condition. The material behavior was examined using, Hardness testing (before and after Heat treatment), corrosion test with dry and wet conditions and surface roughness measurement. Finally, the objective of the project is achieved successfully by the analysis of these results.

Keywords: Aluminum alloy (7076), Pitting corrosion, Hardness testing, Heat treatment.

Acknowledgements

Firstly I would like to thank my Supervisor Mr. Abhishek Mohandas to help me get a lot of information related to this project work and for his feedbacks during the process of report writing and organizing the project.

The amount of knowledge and information that I obtained from him was the pathway to the completion of this work. I would also like to thank Dr. Elansezhian Rasu, Mr.Mutlag, and Mr. Siram for their extended supports on metallic coatings inspection of samples, Hardness testing and roughness measurement at CCE-Mechanical & Dynamic labs.

I would like to thank all the teachers and staff at Caledonian College of Engineering who have made my project work in this college so enjoyable.

TABLE OF CONTENTS

DECLARATION BY THE STUDENT ii Abstract iii Acknowledgements iv List of figures vii List of tables viiiError! Bookmark not defined. CHAPTER 1: INTRODUCTION 1 1.1 Problem statement: 2 1.2 The aim of the project: 2 1.3 The main objectives of the project are 2 1.4 Scope of studies 2 CHAPTER 2: LITERATURE REVIEW 3 2.1 Introduction: 3 2.2 Chapter Summary 4 CHAPTER 3: EXPERIMENTAL SETUP 5 3.1 Introduction: 5 3.2 Samples preparation: 5 3.3 Samples preparation before doing coating done by 6 3.3.1 Numbering of samples 6 3.3.2 Measuring the weight 6 3.3.3 Metalic coating of samples 7 3.3.4 Samples preparation for coating 7 3.3.5 Coatings Procedures 10 3.3.6 Chromium (Cr) coating 10 3.3.7 Zinc spray coating 11 3.4 Heat treatment of coated samples 12 3.4.1 Annealing. 13 3.4.2 Precipitation hardening……………………………………………………….13 3.5 Hardness testing………………………………………………………………..14 3.6 Corrosion test with wet conditions……………….……………………………16 3.7 Surface Roughness Measurement……………………………..……………..18 3.8 Chapter Summary…………………………………………………………..…18 CHAPTER 4 : RESULT AND DISCUSSION 19 4.1 Hardness testing. 19 4.2 Corrosion test with wet conditions 21 4.3 Surface Roughness Measurement. 22 4.4 Chapter Summary……………………………………………………………….24 CHAPTER 5: CONCLUSION 25 CHAPTER 6: RECOMMENDATION AND FUTURE WORK 26 6.1 Recommendation 26 6.2 Future Work 27 References: 28-29

LIST OF FIGURES

List of Figures: Page No

Figure 1.1 Corrosion Circle …………………………….………………….………….…….1

Figure 3.1 Samples before prepared …………………………………..………………….3

Figure 3.2 Samples after prepared …………………..…….…………………………….. 4

Figure 3.3 Paint Remover Acid ……………………………………………………………8 Figure 3.4 Wire Brush ………………………………..……….…………………..……..….9

Figure 3.5 Samples Numbering …………………………………………………….…….10

Figure 3.6 Digital analytical balance…………………………………………….……….. 15

Figure 3.7 Acetone………………………………………………………………….….… 16

Figure 3.8 Samples with acetone……… ……………………………….………….…… 18

Figure 3.9 Distilled water ……………………………..……………………….. …..…….. 20

Figure 3.10 Aluminum paint, Aluminum oxide, Brush and Lab specimen container……………………………………………………………………………………. 21

Figure 3.11 Quantity of Aluminum paint in lab container …………….…..…..……… .21

Figure 3.12 Quantity of oxide Nano powder on Digital analytical balance …………. 21

Figure 3.13 Aluminum Oxide on Mixture Rotary Shaker ……………………..….…. 22

Figure 3.14 Preparation before start and during coating apply ………….……….… 23

Figure 3.15 Sample after coating …………….……………………………………..…… 24

Figure 3.16 Chromium (Cr) coating ………………………………….……………….… 25

Figure 3.17 Samples before Zinc coating………………………………………….…… 26

Figure 3.18 Zinc spray can ……………………………………………..…………….… 27

Figure 3.19 Samples after Zinc coating.………..………………..………………….…. 28

Figure 3.20 Furnace used for annealing process …….…….……….…………….…. 29

Figure 3.21 Furnace used for Precipitation hardening………………….……….…… 30

Figure 3.22 Samples during quenching in cold water………….………………….…. 31

Figure 3.23 Rockwell hardness tester.…………………………….……………….….. 33

Figure 3.24 Different Rockwell Hardness Scales …………………………………….. 35

Figure 3.25 During load selection and Data Display after scale setting ….….…….. 35

Figure 3.26 Coated samples in the test aquarium …………………..……………….. 36

Figure 3.27 Hydrochloric Acid (Hcl).……………………………………………………. 36

Figure 3.28 Preparation of (Hcl) solution ………………………………….……..….. 40

Figure 3.29 Samples during (Hcl) solution reaction …….…………………………….. 40

Figure 3.30 Comparative of Samples weight …….…………………………………….. 40

Figure 4.1 Comparative Hardness scale for Aluminum alloy 7075

before heat treatment…………………………………………………………………… 40

Figure 4.2 Comparative Hardness scale for Aluminum alloy 7075

after heat treatment.…….………………………………………………………………… 40

Figure 4.3 Colum chart of the Removal Rate after168 hours in mm/h after calculated

……………………………………………………………………………………….……… 40

Figure 4.4 Chromium coated surface roughness profile…….…………………..…….. 40

Figure 4.5 Zinc coated surface roughness profile…….………………………………….. 40

Figure 4.6 Aluminum oxide coated surface roughness profile…….……….…………. 40

Figure 4.7 Colum chart of the measurements of surface roughness Rz and Rq in um……………………………………………………………………………………………………………. 40

LIST OF TABLES

List of Tables: Page No

Table 4.1 Comparative Hardness scale for Aluminum alloy 7075 before heat treatment…………………………………………………………………………………5

Table 4.2 Comparative Hardness scale for Aluminum alloy 7075 after heat treatment…………………………….……………………………………………….….6

Table 4.3 Weights of coated samples after 168 hours of corrosion test in Seawater……………….…………………………………………………………….….5

Table 4.4 Parameters of surface roughness Rz and Rq……………………………6

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CHAPTER 1: INTRODUCTION

· Corrosion is the deterioration of materials by chemical interaction with their environment. Corrosion is a metallic cancer that can be controlled by recognizing the early warning signs and by correcting the condition at an early stage. In aerospace sector, Water or water vapour containing salt combines with oxygen in the atmosphere to produce the main source of corrosion in aircraft. Pitting corrosion is one of the major problems faced by aluminum components used in aircraft. In this project an experimental investigation has been taken on the corrosion analysis of aluminum alloy material used in aircraft component.

Figure.1.1 Corrosion Circle

Problem statement:

Due to the high speed heavy landing at a dusty runway. The high potential sand particles has removed the protective coating which lead to subjected the naked metals to sand blasting process allowing pitting corrosion to develop with the assist of oxidation due to the salty atmospheric environment at Seeb air base.

This project focuses on corrosion analysis of aluminum alloy material used in aircraft component.

The aim of the project:

This project provides a study about corrosion analysis of aluminum alloy material used in an aircraft component. Also, Implement corrosion resistance process experimentally. Furthermore, Heat treatment; conducted these operations to change the properties of metals.

The main objectives of the project are:

· To identify the major causes of corrosion.

· Implement corrosion resistance process.

· Analyze the results.

Scope of studies:

· Review most of the literature about corrosion in aluminum alloy material.

· Research on different engineering aspects of corrosion in aluminum alloy material and effect of heat treatment in change of metal properties.

· Study and understand the principle work of the metal coating and heat treatment to reduce the corrosion in aluminum alloy.

· Carry out roughness measurement of the coated samples. Followed by corrosion test with wet condition.

CHAPTER 2: LITERATURE REVIEW

2.1 Introduction:

In this study there are many references works have been referred to:-

As reported by Go swami& Lucadamo (2010) that “the presence of intermetallic precipitation in the alloy matrix improves the mechanical properties of the alloy but leads to a higher susceptibility to local corrosion .Since the second phase particles are usually preferred sites of cathodic or anodic activity. Severe localized attack always occurs due to the galvanic coupling between the active intermetallic phases and the nobler aluminum alloy matrix The alloy intermetallic influence the film structure as well as the corrosion resistance. It is crucial to understand the relative contributions of the solid solution matrix and intermetallic to the film behavior.”

(Go swami & Lucadamo, 2010)

AS suggested by Davis (1999) “relatively pure aluminum presents good corrosion resistance due to the formation of a barrier oxide film that is bonded strongly to its surface (passive layer) and, that if damaged, reforms immediately in most environments; i.e. re-passivation. This protective oxide layer is especially stable in near-neutral solutions of most non-halide salts leading to excellent pitting resistance. Nevertheless, in open air solutions containing halide ions, with Cl- being the most common, aluminum is susceptible to pitting corrosion. This process occurs, because in the presence of oxygen, the metal is readily polarized to its pitting potential and because chlorides contribute to the formation of soluble chlorinated aluminum (Hydr) oxide which interferes with the formation of a stable oxide on the aluminum surface.”

(Davis, 1999)

As indicated by Small man & White (1985)that “Aluminum and its alloys are used in a variety of cast and wrought forms and conditions of heat treatment. For over 70 years, it ranks next to iron and steel in the metal market. The demand for aluminum grows rapidly because of its unique combination of properties which makes it becomes one of the most versatile of engineering and construction material the optimum properties of aluminum are achieved by alloying additions and heat treatments. This promotes the formation of small hard precipitates which interfere with the motion of dislocations and improve its mechanical properties”.

(Small man & White, 1985)

AS stated by Heinz & Cough ran (2000) that “One of the most commonly used aluminum alloy for structural applications is 7075 Al alloy due to its attractive comprehensive properties such as low density, high strength, ductility, toughness and resistance to fatigue. The formation of these micro segregations (hard precipitates) and inherent residual stresses that are associated with their fabrication methods have serious negative effect on their mechanical properties. Hence, this study is aimed at resolving the problems of micro segregations and inherent residual stresses that are associated with aluminum-zinc for improved service performance.”(Heinz& Cough ran, 2000)

This supports Shyann & Chung (2000)“It has been extensively utilized in aircraft structural parts and other highly stressed structural applications. But aluminum-zinc alloy as it is in 7075 Al alloy is susceptible to embrittlement because of micro segregation of MgZn2 precipitates which may lead to catastrophic failure of components produced from it. The alloy is also susceptibility to stress corrosion cracking. This is due to inhomogeneity of the alloy and inherent residual stresses associated with its fabrication methods” (Shyann & Chung, 2000)

As reportedby Adeyemi Dayo & Isa area (2012)that “Since the aluminum and its alloys are widely used in aerospace and automobiles, it is more essential to analyze the wear behavior of alloys. Wear is a removal of material from one or both of two solid surfaces in contact with each other under load and speed. Aluminum alloys of the 7075 series have been considered for structural applications in the automotive industry. The effects of annealing and age hardening heat treatments on the microstructural morphology and mechanical properties of 7075 Al alloy. The alloying elements lead to increase in the strength through formation of MgZn2 precipitate within the structure as the result of aging heat treatment. It was found that yield strength, ultimate tensile strength and hardness values increases but lowers the ductility and impact strength. The significant features of the heat treating process are the solution treatment temperature, the quench rate, the aging temperature and again time”. (Adeyemi Dayo & Isa area, 2012)

As reported by Juffs & Hughes (2001) that” The surface of a wrought or cast alloy is

likely to contain not only aluminum oxide alone, but may for example contain a fragment of a mixed Al-Mg oxide for alloys rich in Mg. This is primarily because of the heat of segregation of Mg is high and it has a favorable free energy for oxide formation. If however an Al surface is mechanically undisturbed – then the surface oxide is relatively protective. Though, most real surfaces have some sort of mechanical finishing which results in the formation of a near surface deformed layer (NSDL) and shingling. Shingling occurs where the alloy matrix is spread across the surface including IM particles in abrasion and milling. (Juffs & Hughes, 2001)

As noted by Aremo & Adeyemi (2012) that “aluminum and its alloys are used in a variety of cast and wrought forms and conditions of heat treatment. For over 70 years, it ranks next to iron and steel in the metal market. The demand for aluminum grows rapidly because of its unique combination of properties which makes it becomes one of the most versatile of engineering and construction material. The optimum properties of aluminum are achieved by alloying additions and heat treatments. This promotes the formation of small hard precipitates which interfere with the motion of dislocations and improve its mechanical properties. One of the most commonly used aluminum alloy for structural applications is 7075 Al alloy due to its attractive comprehensive properties such as low density, high strength, ductility, toughness and resistance to fatigue. It has been extensively utilized in aircraft structural parts and other highly stressed structural applications. But aluminum-zinc alloy as it is in 7075 Al alloy is susceptible to embrittlement because of micro segregation of MgZn2 precipitates which may lead to catastrophic failure of components produced from it. The alloy is also susceptibility to stress corrosion cracking. This is due to inhomogeneity of the alloy and inherent residual stresses associated with its fabrication methods”. (Aremo& Adeyemi, 2012)

Chapter 1 Introduction

2.2 Chapter Summary

This section included past studies and works in corrosion investigation and implement corrosion resistance process. The presence of intermetallic precipitation in the alloy matrix improves the mechanical properties of the alloy and were utilized as a part of this task as result and direction, on the grounds that it is vital to allude to old studies and attempts to expand the effectiveness of the venture.

Chapter 2 Literature Review

CHAPTER 3: EXPERIMENTAL SETUP

3.1 Introduction:

This study is concerned with treatment of the corrosion, which affects the outer layer of aluminum alloy using three different types of metal coating, and to study the effect of heat-treating operation on the corrosion resistance process. Likewise will be the work to reduce the occurrence of disasters resulting from corrosion which may affect the components, especially in the aviation sector because the human and material losses would be extremely critical. In this project, investigations are carried out by:

· Applying three different types of metallic coating.

· Heat treatment of coated samples (3 numbers, 1 from each coating type).

· Hardness testing (before and after Heat treatment).

· Corrosion test with wet condition.

· Surface roughness measurement.

3.2 Samples preparation:

In the beginning, samples are prepared in correct dimension of “20mm*20mm” and “50 mm *50 mm “.

Figure 3.1 Samples before prepared. Figure 3.2 Samples After prepared.

Followed by, surface preparation/cleaning of samples is done with wire brush and paint remover acid.

  Figure 3.3 Paint Remover Acid Figure 3.4 Wire Brush

3.3 Samples preparation before doing coating done by:

Numbering of samples:

Basic method of numbering systems is included, that is important to know and identify the samples after coating in extraction of results.

Figure 3.5 Samples Numbering

Measuring the weight:

Weighing the samples before and after the coating to get the difference in weight by using digital analytical balance as shown in figures below.

Figure 3.6 Digital analytical balance

METALLIC COATINGS OF SAMPLES:

I used mainly 3 types of metallic coatings in this project. They are Nano aluminum oxide (Al2o3), Chromium (Cr) and zinc coating.

Sample preparation for coating:

Surface preparation is the vital first step treatment of a substrate before the application of any coating. The performance of a coating is significantly affected by its ability to obey properly to the substrate material. It is usually well recognized that precise surface preparation is the most series factor affecting the total success of surface treatment. The existence of even small quantities of surface contaminants, grease, cutting oil, oxides etc. can physically damage and decrease coating adhesion to the substrate. The following are the procedures of samples preparation:

· Using personal protective equipment (PPE) to reduce our exposure to hazards.

· Cleaning the samples by using acetone, followed that by using distilled water as shown in figures below.

Figure 3.7 Acetone and Cleaning samples with acetone

Figure 3.8 Samples with Acetone Figure 3.9 Distilled water

· Prepare a mixture of 50 ml of aluminum paint with 0.500 (g) of aluminum oxide in Lab specimen container then put the container on the rotary shaker for two hours until the mixing process well. As shown in figures below.

Figure 3.10 Al, paint, Al, oxide, Figure 3.11 Quantity of Al paint in lab container Brush and Lab specimen container.

Figure 3.12 Quantity of oxide Nano powder on Digital analytical balance

Figure 3.13 Aluminum Oxide on Mixture Rotary Shaker

Coatings Procedures:

Aluminum oxide layer above the aluminum samples is to prevent oxygen and water, which they are in the air, to contact the metal located below them. So that is going to stop the oxidation process at an early stage. The following are the steps of samples coating with Aluminum oxide:

1. After cleaning the samples, followed by scratching process to them with emery paper to let coating layer contact with samples metal.

2. Equally apply the aluminum oxide mixture to all sides of the samples.

3. Expose coated samples to exposure area for dry to a period of time about 2 hours.

4. Repeat steps (1),(2)and (3) until obtain the proper thickness of aluminum oxide coating on the samples.

Figure 3.14 Preparation before start and During coating apply

Figure 3.15 Sample after coating

Chromium (Cr) coating:

Chrome coating is used to provide a very high degree of hardness on the surface of a metal to improve wear resistance, reduce friction, and in some cases, improve corrosion resistance. Chrome coating is an electrolytic process that can be applied to regular aluminum, and other materials. This case details the applying of chrome coating to aluminum alloy surfaces as shown in figure 3.16.

1. Proper cleaning of the samples prior to coating.

2. Surfaces after coating should be homogeneous and uniform in color.

Samples before (Cr) coating Samples after (Cr) coating

Figure 3.16 Chromium (Cr) coating

Zinc spray coating:

Zinc spray provides all metals surfaces; it forms a quick draying, adhesive, protective layer of micro fine flakes. Metal parts sprayed with zinc spray showed no corrosion even after more than 550 hours. The innovative zinc flakes form a highly protective layer even against extreme weather and environmental influences.

Following procedures were carried out for zinc spray coating process:

1. Shake can before use until the mixing ball can be heard clearly.

2. Spray on evenly and crosswise at room temperature and at about 25 cm distances from the surface.

3. Dust-dry after approx. 15 minutes, fully hardened after approx. 10-12 hours.

4. Repeat steps (2) and (3) until obtain the proper thickness of zinc spray on the samples.

Figure 3.17 Samples before Zinc coating Figure 3.18 Zinc spray can

Figure 3.19 Samples after Zinc coating

3.4 Heat treatment of coated samples (3 samples, 1 from each coating type):

The heat treatment contains heating and cooling operations or the sequence of two or more such operations applied to any material in order to modify its metallurgical structure and change its physical, chemical and mechanical properties. In this project have been used two types of heat treatment to investigate the effects of annealing and precipitation hardening heat treatment on the hardness, and impact strength of aluminum alloy7075, details as follows:

Apparatus:

· Furnace.

· Bath with Cold Water.

· Long Reach Hose Grip Pliers to hold the samples.

· Watch.

· Gloves.

Annealing :

Metallographic and hardness test piece samples to 470 °C, soaking them at this temperature for 2 hours and then furnace cooled. As shown in figure below.

Figure 3.20 Furnace used for annealing process

Precipitation hardening:

Metallographic and hardness test piece samples at a temperature of 465 °C for 2 hours followed by rapid quenching in cold water. These quenched samples were then subjected to a precipitation hardening treatment (age hardening) by heating them to 120 °C, holding them at this temperature for 3 hours and then followed by air cooling to room temperature. As shown in figures below.

  Figure 3.21 Furnace used for Precipitation hardening.

Figure 3.22 During Quenching in cold water

3.5 Hardness testing (before and after Heat treatment):

Figure 3.23 Rockwell hardness tester.

This test is done with Rockwell hardness test. It is characterizes the indentation Hardness of materials (Al 7075) through the scale of penetration of a diamond come or hardened steel ball indenter, loaded on a material test-piece. It is one of several definitions of hardness in material science.

· Procedures of Test :

1. Select the proper scale from Rockwell hardness scale plate been displayed on the device to suit to aluminum alloy samples. The scale is consisting of the correct indicator and load.

2. Place the surface area to be measured close to the indenter. It is important for the accuracy of the test that the sample

be held securely during the application of load.

3. Slowly move down the anvil of device to touch flat surface of the sample, therefore automatic display of the Rockwell hardness number on its screen.

4. Repeat step (3) in various parts of test samples, then take the average of readings been taken.

Figure 3.24 Different Rockwell Hardness Scales

Figure 3.25 During load selection and Data Display after scale setting

3.6 Corrosion test with wet conditions:-

Test in sea water depends on the simulation of the actual environmental conditions being experienced by the metal, this is widely variable environmental conditions, as controlled by the temperature, the amount of dissolved oxygen, type and amount of biological pollution and natural reproduction of microbes.

In this test ,a total of 4 samples of 3 different coatings and one without coating were completely immersed in an aquarium contains seawater with oxygen supply for 7 days at room temperature .Followed by, followed by treatment of the samples with solution of Hydrochloric Acid (Hcl) and water to get proper readings of weight. Therefore, to obtain data for comparison with weight loss corrosion data.

· Procedures of Test :

1. Put the samples in the aquarium and fill it with a certain amount of sea water.

2. Provide an oxygen to the aquarium during test by using electrical air pump.

3. Leave the Samples for a period of 7 days, then take it out and observe the results.

4. Solution is prepared (9:1), 100ml of Hydrochloric Acid (Hcl) and 900ml of (water) H2O.

5. Coated samples were treated with Hcl solution for 5 minutes.

6. Measure the weight of all samples after test by using digital analytical balance, monitor loss of weight.

Figure 3.26 Coated samples in the test aquarium.

Figure 3.27 Hydrochloric Acid (Hcl). Figure 3.28 Preparation of solution Figure 3.29 During solution reaction

   Initial weight Weight after test After Hcl treatment

Figure 3.30 Comparative of Samples weight

3.7 Surface Roughness Measurement:

The most important parameter describing surface integrity is surface roughness. Surface must be within certain limits of roughness. Therefore, measuring surface roughness is vital to quality control of machining work piece. In this test, we have been used Statistical descriptors for measuring roughness of samples.

3.8 Chapter Summary:

This chapter is talked about seven different types of tests and tasks which are:

initial samples preparation, samples preparation for coating, three different types of coatings procedures, two different types of Heat treatment to coated samples, Hardness testing (before and after Heat treatment), Corrosion test in seawater and Surface Roughness Measurement. Each one of those tests and tasks contains subtle elements of the methodology and obliged strategy.

Chapter 3 Experimental Setup

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CHAPTER 4: RESULT AND DISCUSSION

This project is consisting of two major steps of experiments namely:

· Implement corrosion resistance process.

· Investigation & Analysis of the results.

Each experiment will be discussed clearly with investigation of their results.

4.1 Hardness testing (before and after Heat treatment):

As previously been explained for this test in the third chapter of this project, it was concluded that the hardness of aluminum increases after heat treatment process than before and the following results as in tables below,

Type of coatingReading 1 in (g)Reading 2 in (g)Reading 3 in (g)Average Readingsin (g)
zinc9597.792.194.93
aluminum8588.48686.46667
chrome89.388.485.287.63333
Al without coating85.286.68786.26667

Table 4. 1 Comparative Hardness scale for Aluminum alloy 7075 before heat treatment

Type of coatingReading 1 in (g)Reading 2 in (g)Reading 3 in (g)Average Readingsin (g)
zinc104101.3100101.7667
aluminum8889.79089.23333
chrome89.689.486.788.56667
Al without coating85.286.68786.26667

Table 4. 2 Comparative Hardness scale for Aluminum alloy 7075 after heat treatment

Figure 4.1 Comparative Hardness scale for Aluminum alloy 7075

before heat treatment.

Figure 4.2 Comparative Hardness scale for Aluminum alloy 7075

after heat treatment.

Through graphics above we notice that, hardness of sample been coated with chrome was more than others after heat treatment, therefore it improves properties of metal in corrosion resistance.

4.2 Corrosion test with wet conditions:

As previously been explained for this test in the chapter three of this project, it was concluded that samples of aluminum after 168 hours start loss of their weight with different types of coating and the following results as in tables below,

Type of coatingInitial weight (g) of samples before testingWeight (g) of samples after 168 hours of testingRemoval Rate in mm/hAfter calculated
zinc27.17427.0950.264
aluminum24.82924.8230.00452
chrome19.3319.2520.0696
Al without coating20.12920.0350.0815

Table 4. 3 Weights of coated samples after 168 hours of corrosion test in Seawater

Figure 4. 4 Colum chart of the Removal Rate after168 hours in mm/h after calculated

From these results in terms of taking weights of tested samples by Digital analytical balance, we note that the sample with zinc coating was lost weight more than other comparative samples, while the sample coated with aluminum oxide lost the least weight and this shows it is the most resistant to corrosion.

4.3 Surface Roughness Measurement:

As previously been explained for this test in the chapter three of this project, it was concluded that by Surface Roughness Tester measured the surface roughness of samples gives root mean square deviation of the profile (Rq) and ten-point mean roughness (Rz), following results as in tables below :

Type of coatingRzRq
zinc65.9918.22
aluminum8.452.70
chrome0.250.05

Table 4. 4 Parameters of surface roughness Rz and Rq

Figure 4. 5 Chromium coated surface roughness profile

Figure 4. 2 Zinc coated surface roughness profile

Figure 4. 7 Aluminum oxide coated surface roughness profile

Figure 4. 8 Colum chart of the measurements of surface roughness Rz and Rq in um

Through these results it is clear to us that the surface roughness of the sample with chrome coating is softer when compared to the rest of samples, and thus less likely to be friction which leads to the metal corrosion. On the other side, we found that sample with zinc coating was more surface roughness.

4.4 Chapter Summary:

This chapter is talked about results of all tests and tasks been carried out in this project which are:

Heat treatment to coated samples, Hardness testing (before and after Heat treatment), Corrosion test in seawater and Surface Roughness of coated samples. All scientific experiments are acceptable in terms of objective and iterative, where it does not affect the results if we repeated these experiments again and this ensures that the test or its result not be random and occur once.

Chapter 4 Result and Discussion

CHAPTER 5: CONCLUSION

The purpose of this project provides a study about corrosion analysis of aluminum alloy material used in an aircraft component. This is possible only by resisting the corrosion in aircraft components happens at high speed heavy landing at a dusty runway. The high potential sand particles has removed the protective coating which lead to subjected the naked metals to sand blasting process allowing pitting corrosion to develop with the assist of oxidation due to the salty atmospheric environment at Seeb Air Base.

The objectives of this project were achieved by three steps, identifying the major causes of corrosion, implement corrosion resistance process and analyze the results perfectly. I used three different types of coating followed by different types of testing for its analysis. The heat treatment of coated samples proved that hardness of sample been coated with chrome was more than others after heat treatment, therefore it improves properties of metal in corrosion resistance. Furthermore, results showed that sample with zinc coating was lost weight more than other comparative samples, while the sample coated with aluminum oxide lost the least weight and this shows it is the most resistant to corrosion. Also results showed that sample with chrome coating is softer when compared to the rest of samples, and thus less likely to be friction which leads to the metal corrosion. On the other side, we found that sample with zinc coating was more surface roughness.

Metal coatings and their thickness are vital in making the samples resist corrosion. From corrosion test results, it’s been noticed that samples with aluminum oxide coated sample showing the least corrosion values. These results and their comparisons are used for achieving the objectives of this project successfully.

Chapter 5 Conclusion

CHAPTER 6: RECOMMENDATIONS AND FUTURE WORK

6.1 Recommendation

The following details will explain the major issues and the recommendations in relation with this project work:

· Difficulty in finding specimens of the same parts used in aircraft but after a try has been taking a permit to use them for study purpose. Initial approval prior to starting work is recommended for the availability of materials.

· Time was not enough to carry out corrosion test with dry condition, so the time frame for the project execution has to be planned accordingly.

· Difficulty to find all the types of coating required to carry out coating process.

· Difficulty to carry out erosion tests due to the small sample size and therefore advised to increase their size.

6.2 Future Work

The current work has investigated some aspects of corrosion testing for Aluminum alloy using in aircraft components. However, there is still a room to conduct the corrosion analysis in terms of chemical and material properties. Few of such suggestions are listed below so that they can be carried out as an extension of this project work, so that key findings of this work could be justified.

· Analysis by optical microscopy, will conducted to help elucidate corrosion initiation sites, and degradation of coating.

· For corrosion test with dry condition, samples will be removed and analyzed for a longer exposure period.

· Conducting the same work using different metallic coating so that key results could be compared and a more relevant material coating could be identified.

References:

Royal Air Force of Oman, 2014.Corrosion prevention

And control manual. Lockheed Martin Corporation.

Mahesh, B. & Raman, R., 2014. Role of Nanostructure in Electrochemical Corrosion and High Temperature Oxidation: A Review. The Minerals, Metals & Materials Society and ASM International.45 (A). p. 5799-5818.

Tahamtan, S. & Halvaee, A., 2013.Fabrication of Al/A206–Al2O3 nano/micro composite by combining ball milling and stir casting technology. Mater Des 49:347

Pacheco, T., 1997.A comparison of two Nextel 440 fiber reinforced aluminum composites using acoustic emission. J Mater Sci 32:3135–3142

Parker, E., 1999. Pipe Line Corrosion and cathodic Protection.3rd edition.USA: Elsevier science.

Davis, J.R., 1999.Corrosion of Aluminum and Aluminum alloys.1St edition.USA: ASM International.

Newman Roger, 1976. Pitting Corrosion of Metals.

[Online]. Available from: http://www.electrochem.org/dl/interface/spr/spr10/spr10_p033-038.pdf. [Accessed: 27 Nov 2015].

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2 Chromium Reading 1 Reading 2 Reading 3 Average Reading 95 97.7 92.1 94.93 5 aluminum Oxide Reading 1 Reading 2 Reading 3 Average Reading 85 88.4 86 86.466666666666654 1 Zinc Reading 1 Reading 2 Reading 3 Average Reading 89.3 88.4 85.2 87.633333333333326 4 Al,with Out coating Reading 1 Reading 2 Reading 3 Average Reading 85.2 86.6 87 86.266666666666666 2 Chromium Reading 1 Reading 2 Reading 3 Average Reading 104 101.3 100 101.76666666666667 5 aluminum Oxide Reading 1 Reading 2 Reading 3 Average Reading 88 89.7 90 89.233333333333334 1 Zinc Reading 1 Reading 2 Reading 3 Average Reading 89.6 89.4 86.7 88.566666666666663 4 Al,with Out coating Reading 1 Reading 2 Reading 3 Average Reading 85.2 86.6 87 86.266666666666666 Removal Rate in mm/h After calculated zinc aluminum chrome Al without coating 0.26400000000000001 4.5199999999999997E-3 6.9599999999999995E-2 8.1500000000000003E-2

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