A Study of Corrosion Rate of AISI 304 and AISI 316 Stainless Steels in Hydrochloric Acid, Sulfuric Acid

and Dead Sea Water

Submitted In the Partial Fulfillment of the Requirements for the Degree of B.Sc

In

Industrial Engineering

At

Jordan University of Science and Technology

StudentMohammad Ahmad Gharaibeh

20040029019

SupervisorDr. Mohammed Hayajneh

ExaminersProf. Adel M. Hassan

Dr. Abdullah Al-Rashdan

Fall Semester 2008/2009

ACKNOWLEDGEMENT

To my brother Faris, who helped me to build this project step by step, he provided me

with materials used during the work in this experiment.

Special thanks to Engineer Ameen Malkawy, because of his commitment in all

our scheduled meetings with no hesitation to provide me with any

information I need.

And for my friend Mutaz Darabseh because of his great help by

providing me by some books, and for his encouragement to complete this

project.

Finally to my supervisor Dr. Mohammed Hayajneh, who guided me to

get this project, by his advices during this work.

ABSTRACT

This project aimed to compare the corrosion resistance behavior of AISI 316 and AISI 304

stainless steels in the hydrochloric acid, sulfuric acid and the Dead Sea water. Several

specimens of steels were immersed in different concentration of the acids and in the Dead

Sea water, for a period of three months, the mass was measured weekly. The results showed

that the acid concentration increases the mass loss when it increases. Also; the Hydrochloric

acid is more corrosive than the Sulfuric acid and the Dead Sea water, and the AISI 304

Stainless steel more resistive to chemicals and water used than the AISI 316 stainless steel.

LIST OF TABLES

Table Page

Table 1. Comparison between slopes of the acids curves effecting on AISI 304. 23

Table 2. Comparison between slopes of the acids curves effecting on AISI 316. 24

Table B1. Chemical Composition of AISI 304. 33

Table B2. Mechanical Properties of AISI 304. 33

Table B3. Thermal Properties of AISI 304. 33

Table B4. Electrical Properties of AISI 304. 34

Table B5. Chemical Composition of AISI 316. 34

Table B6. Mechanical Properties of AISI 316. 34

Table B7. Thermal Properties of AISI 316. 35

Table B8. Electrical Properties of AISI 316. 35

Table C1. Properties of Hydrochloric Acid. 37

Table C2. Properties of Sulfuric Acid. 38

LIST OF FIGURES

Figure Page

Figure 1. The experimental setup: steels, medium and plastic container. 12

Figure 2. The sensitive balance showing 0.1 mg precision. 13

Figure 3. The effect of HCl on AISI 304 at different concentrations 14

Figure 4. The effect of HCl on AISI 316 at different concentrations 15

Figure 5. The effect of H2SO4 on AISI 304 at different concentrations 16

Figure 6. The effect of H2SO4 on AISI 316 at different concentrations 17

Figure 7. The effect of HCl on AISI 316 and AISI 304 at 0.1M 18

Figure 8. The effect of HCl on AISI 316 and AISI 304 at 0.3M 18

Figure 9. The effect of HCl on AISI 316 and 304 at 0.7M 19

Figure 10. The effect of H2SO4 on AISI 316 and AISI 304 at 0.1M 20

Figure 11. The effect of H2SO4 on AISI 316 and AISI 304 at 0.3M 21

Figure 12. The effect of H2SO4 on AISI 316 and AISI 304 at 0.7M 21

Figure 13. The effect of HCl and H2SO4 on AISI 304 22

Figure 14. The effect of HCl and H2SO4 on AISI 316 23

Figure 15. The effect of the Dead Sea water on AISI 316 and AISI 304 24

NOMENCLATURE

Symbols

ao Y-axis intercept g

a1 Coefficient of X mg/week

a2 Coefficient of X2 mg/week2

a3 Coefficient of X3 mg/week3

b Slope of the linear function mg/week

R2 Coefficient of determination -

St The total sum of squared the residuals between the data points and the

mean. g2

Sr The sum of squared residuals between the data points and regression curve. g2

X Time Week

Y Specimen Mass g

Abbreviations

AISI 304 AISI 304 stainless steel

AISI 316 AISI 316 stainless steel

HCl Hydrochloric Acid

H2SO4 Sulfuric Acid

M Molar

TABLE OF CONTENTS

Title Page

1. INTRODUCTION 1

2. THEORY 3

2.1 CORROSION AND CORROSION RESISTANCE 3

2.2 MATHEMATICAL APPROACH 9

3. EXPERIMENTAL DETAILS 11

4. RESULTS AND DISCUSSIONS 14

4.1 THE EFFECTS BASED ON THE ACIDS CONCENTRATION 14

4.2 THE EFFECTS BASED ON THE STEEL TYPE 17

4.3 THE EFFECTS BASED ON THE ACID USED 22

5. CONCLUSIONS 26

6. RECOMMENDATIONS 27

7. REFERENCES28

APPENDIX A 29

APPENDIX B 32

APPENDIX C 36

1. INTRODUCTION

Many industrial applications especially in chemical plants, such as fertilizer factories,

have harsh environments such as hydrochloric acid and sulfuric acid. Also in Jordan many

plants use the Dead Sea water in their processes like the salt producing plants.

So, this project aimed to compare the anti-corrosive behavior of the stainless steels AISI

304 and AISI 316 against these acids and the Dead Sea water, we selected the stainless steels

because they resist corrosion; this achieved by dissolving sufficient chromium in the iron to

produce film on the surface which isolates protects the steel from corrosion.[1,2]

The stainless character occurs when the concentration of chromium exceeds about 12

wt%. However, even this is not adequate to resist corrosion in acids such as HCl or H2SO4;

higher chromium concentrations and the judicious use of other solutes such as molybdenum,

nickel and nitrogen is then needed to ensure a robust material [3].

There are requirements other than corrosion which have to be considered in

engineering design. For this reason, there is a huge variety of alloys available, but they can

be classified into four main categories [4]:

hardenable stainless steels;

ferritic stainless steels;

austenitic stainless steels;

Duplex stainless steels.

Many researches are now took place to improve the chemical and surface properties of

solid materials. Such as increasing the corrosion resistance, etching and cleaning. [5]. But

this project has no surface properties improvement.

The representations of corrosion resistance of steels due to the acids are investigated by

the mass loss rate. The regression techniques were performed in this work after the masses

are plotted on many figures to get the best fit to these data points according to the coefficient

of determination, the following paragraphs will illustrate the experiment used in this project

in a clear manner.

2. THEORY

The theoretical background in this project is divided into two main categories the first

one is the corrosion and the corrosion resistance and the other one is the mathematical

“statistical”, by using the techniques of least square regression to fit the data into good fits

according to the coefficient of determination R2.

2.1 CORROSION AND CORROSION RESISTANCE

The corrosion of metals has many definitions, one of them defining it as the destructive

and unintentional attack of a metal; it is electrochemical and ordinarily begins at the surface

[4], another definition says it is breaking down of essential properties in a material due to

chemical reactions with its surroundings [6], and a wide definition tells it is the erosion by

chemical reaction [7]. So from these three definitions we can summarize the principle of

corrosion as a chemical action that causes the gradual deterioration of the surface of a metal

by oxidation or chemical reaction [7].

The problem of metallic corrosion is one of significant proportions; in

economic terms, it has been estimated that approximately 5% of an

industrialized nation’s income is spent on corrosion prevention and the

maintenance or replacement of products lost or contaminated as a result

of corrosion reactions. The consequences of corrosion are all too common.

Familiar examples include the rusting of automotive body panels and

radiator and exhaust components [4].

Corrosion processes are occasionally used to advantage. For

example, etching procedures make use of the selective chemical

reactivity of grain boundaries or various microstructural constituents [4].

For metallic materials, the corrosion process is normally

electrochemical, that is, a chemical reaction in which there is transfer of

electrons from one chemical species to another. Metal atoms

characteristically lose or give up electrons in what is called an oxidation

reaction. For example, the hypothetical metal M that has a valence of n

(or n valence electrons) may experience oxidation according to the

reaction [4]

M Mn+ + ne- (1)

In which M becomes an n+ positively charged ion and in the process

loses its n valence electrons; e- is used to symbolize an electron.

Examples in which metals oxidize are

Fe Fe+2 + 2e- (2)

Al Al+3 + 3e- (3)

The site at which oxidation takes place is called the anode; oxidation

is sometimes called an anodic reaction [4].

The electrons generated from each metal atom that is oxidized must

be transferred to and become a part of another chemical species in what

is termed a reduction reaction. For example, some metals undergo

corrosion in acid solutions, which have a high concentration of hydrogen

(H+) ions; the H+ ions are reduced as follows:

2H+ + 2e- H2 (4)

and hydrogen gas (H2) is evolved.

Other reduction reactions are possible, depending on the nature of

the solution to which the metal is exposed. Or an acid solution having

dissolved oxygen, as we used in this project, reduction according to

O2 + 4H+ + 4e- 2H2O (5)

Any metal ions present in the solution may also be reduced; for ions

that can exist in more than one valence state (multivalent ions), reduction

may occur by

Mn+ + e- M(n-1)+ (6)

in which the metal ion decreases its valence state by accepting an

electron. Or a metal may be totally reduced from an ionic to a neutral

metallic state according to

Mn+ + ne- M (7)

The location at which reduction occurs is called the cathode.

Furthermore, it is possible for two or more of the reduction reactions

above to occur simultaneously.

An overall electrochemical reaction must consist of at least one

oxidation and one reduction reaction, and will be the sum of them; often

the individual oxidation and reduction reactions are termed half-reactions.

There can be no net electrical charge accumulation from the electrons

and ions; that is, the total rate of oxidation must equal the total rate of

reduction, or all electrons generated through oxidation must be consumed

by reduction [1].

The variables in the corrosion environment, which include fluid

velocity, temperature, and composition, can have a decided influence on

the corrosion properties of the materials that are in contact with it. In

most instances, increasing fluid velocity enhances the rate of corrosion

due to erosive effects. The rates of most chemical reactions rise with

increasing temperature; this also holds for the great majority of corrosion

situations. Increasing the concentration of the corrosive species (e.g., H+

ions in acids) in many situations produces a more rapid rate of corrosion.

However, for materials capable of passivation, raising the corrosive

content may result in an active-to-passive transition, with a considerable

reduction in corrosion [4].

Cold working or plastically deforming ductile metals is used to

increase their strength; however, a cold-worked metal is more susceptible

to corrosion than the same material in an annealed state. For example,

deformation processes are used to shape the head and point of a nail;

consequently, these positions are anodic with respect to the shank region.

Thus, differential cold working on a structure should be a consideration

when a corrosive environment may be encountered during service [2].

It is convenient to classify corrosion according to the manner in

which it is manifest. Metallic corrosion is sometimes classified into eight

forms: uniform, galvanic, crevice, pitting, intergranular, selective

leaching, erosion–corrosion, and stress corrosion. The causes and means

of prevention of each of these forms will be discussed briefly [1].

Uniform attack is a form of electrochemical corrosion that occurs with

equivalent intensity over the entire exposed surface and often leaves

behind a scale or deposit. In a microscopic sense, the oxidation and

reduction reactions occur randomly over the surface. Some familiar

examples include general rusting of steel and iron and the tarnishing of

silverware. This is probably the most common form of corrosion. It is also

the least objectionable because it can be predicted and designed for with

relative ease [8].

Galvanic corrosion occurs when two metals or alloys having different

compositions are electrically coupled while exposed to an electrolyte. This

is the type of corrosion or dissolution. The less noble or more reactive

metal in the particular environment will experience corrosion; the more

inert metal, the cathode, will be protected from corrosion. For example,

steel screws corrode when in contact with brass in a marine environment;

or if copper and steel tubing are joined in a domestic water heater, the

steel will corrode in the vicinity of the junction [4,8].

The corrosion occurs in crevices and recesses or under deposits of

dirt or corrosion products where the solution becomes stagnant and there

is localized depletion of dissolved oxygen is called crevice corrosion. The

crevice must be wide enough for the solution to penetrate, yet narrow

enough for stagnancy; usually the width is several thousandths of an inch.

Electrochemical corrosion occurs here as a consequence of concentration

differences of ions or dissolved gases in the electrolyte solution, and

between two regions of the same metal piece [2,4 ,8].

Pitting is another form of much localized corrosion attack in which

small pits or holes form. They ordinarily penetrate from the top of a

horizontal surface downward in a nearly vertical direction. It is an

extremely insidious type of corrosion, often going undetected and with

very little material loss until failure occurs [1,8].

Intergranular corrosion occurs preferentially along grain boundaries

for some alloys and in a specific environment. The net result is that a

macroscopic specimen disintegrates along its grain boundaries. This type

of corrosion is especially prevalent in some stainless steels. When heated

to temperatures between 500 and 800oC (950 and 1450oF) for sufficiently

long time periods, these alloys become sensitized to intergranular attack.

It is believed that this heat treatment permits the formation of small

precipitate particles of chromium carbide Cr23C62 by reaction between the

chromium and carbon in the stainless steel. These particles form along

the grain boundaries both the chromium and the carbon must diffuse to

the grain boundaries to form the precipitates, which leaves a chromium-

depleted zone adjacent to the grain boundary. Consequently, this grain

boundary region is now highly susceptible to corrosion. Intergranular

corrosion is an especially severe problem in the welding of stainless

steels, when it is often termed weld decay [1,2,4,8].

Selective leaching is found in solid solution alloys and occurs when

one element or constituent is preferentially removed as a consequence of

corrosion processes. The most common example is the dezincification of

brass, in which zinc is selectively leached from a copper–zinc brass alloy.

The mechanical properties of the alloy are significantly impaired, since

only a porous mass of copper remains in the region that has been

dezincified. In addition, the material changes from yellow to a red or

copper color. Selective leaching may also occur with other alloy systems

in which aluminum, iron, cobalt, chromium, and other elements are

vulnerable to preferential removal [4].

Erosion–corrosion arises from the combined action of chemical attack

and mechanical abrasion or wear as a consequence of fluid motion.

Virtually all metal alloys, to one degree or another, are susceptible to

erosion–corrosion. It is especially harmful to alloys that passivate by

forming a protective surface film; the abrasive action may erode away the

film, leaving exposed a bare metal surface. If the coating is not capable of

continuously and rapidly reforming as a protective barrier, corrosion may

be severe. Relatively soft metals such as copper and lead are also

sensitive to this form of attack. Usually it can be identified by surface

grooves and waves having contours that are characteristic of the flow of

the fluid [7].

Stress corrosion, sometimes termed stress corrosion cracking, results

from the combined action of an applied tensile stress and a corrosive

environment; both influences are necessary. When a stress is applied,

small cracks form and then propagate in a direction perpendicular to the

stress, with the result that failure may eventually occur. Failure behavior

is characteristic of that for a brittle material, even though the metal alloy

is intrinsically ductile. Most alloys are susceptible to stress corrosion in

specific environments, especially at moderate stress levels [1,8].

2.2 MATHEMATICAL APPROACH

In this section of our project the techniques of the least square regressions are used in

order to fit the data points into good fits according to the value of the coefficient of

determination R2.

The linear regression in the form of [9]

Y= bX + ao (8)

Where:

b: the slope of the linear function,

ao: the Y-axis intercept.

The third order polynomial is also used in the coming paragraphs in the form of [9]

Y= ao + a1X + a2X2 + a3X3 (9)

Where:

ao, the Y-axis intercept.

a1, a2 and a3 are the coefficients of the variables X, X2and X3respectively .

To examine whether the fit is good or poor we used the coefficient of determination R2.

The following formula will describe the mathematical illustration [9]

, (10)

Where:

St: is the total sum of the squared residuals between the data points and the mean.

Sr: is the sum of the squared residuals between the data points and the regression curve.

For full derivation, see Appendix A.

3. EXPERIMNTAL DETAILS

For this project seven similar specimens have been selected with dimensions of 4×7 cm

and 2 mm thickness, for each type of steel 7 specimens, these specimens to be arranged as

the following:

1. Three specimens for HCL in purity of 98.7% :

One at 0.1 molar concentration of HCL.

One at 0.3 molar concentration of HCL.

One at 0.7 molar concentration of HCL.

2. Three specimens for H2SO4 in purity of 98.3%:

One at 0.1 molar concentration of H2SO4.

One at 0.3 molar concentration of H2SO4.

One at 0.7 molar concentration of H2SO4.

3. One specimen to be used for the Dead Sea water.

These specimens were immersed in 100 ml of concentration mentioned above, and 500

ml for pieces immersed in Dead Sea water, and they were contained in a plastic container.

See figure 1.

Figure 1. The experimental setup: steels, medium and plastic container.

The mass was measured weekly, after removing the specimens from solutes using a

cheap plastic grabber; the specimens are dried using a clean dry cloth the left 10 minutes to

assure the dryness conditions of them, to avoid weighing the acids or water, and then using a

sensitive electronic balance (figure 2) with precision of 0.1 mg (0.0001 grams) the mass are

weighed and the data results are recorded, this operation was done during three months for

the steels immersed in acids and two months to the steels immersed in Dead Sea water.

Figure 2. The sensitive balance showing 0.1 mg precision.

Then the data points are collected and plotted on different figures using the MS-Excel

software, now we can analyze and compare those data.

4. RESULTS AND DISCUSSIONS

In this chapter 13 figures will be discussed in order to conclude the results of our

project, the equations appear in the figures are fitted using the MS-Excel.

4.1 THE EFFECTS BASED ON THE ACIDS CONCENTRATION

The following 4 figures will show us the corrosive effect of the acid concentrations on

the steels, 2 figures for HCl and 2 figures for H2SO4.

Figure 3. The effect of HCl on AISI 304 at different concentrations.

From the figure above it is clearly seen that is the higher concentration of HCl is the

higher corrosive effect (mass loss) in the steels specimens, a fit of third order polynomial is

used for the three curves, the equations and coefficient of determinations appear on the

different curves, the values or R2 represents that is the fit used fit is good one. At the higher

concentration (0.7M) the loss in mass starts in a rapid mode (up to week 5) and then it

reduced in the next weeks.

Figure 4. The effect of HCl on AISI 316 at different concentrations.

Here also we can see that the higher HCl concentration is the higher corrosive effect on

the AISI 316 steel specimens, a linear regression is used here which provides a good fit

according to the R2 values. An observation is clear here, at low concentrations (0.1 M) the

slope is very low (-25.4 mg/week) but at the high concentration (0.7 M) it was (-399.7

mg/week), it is a sharp increase shown here.

Figure 5. The effect of H2SO4 on AISI 304 at different concentrations.

A strange phenomenon occurred here, the lowest concentration of H2SO4 (0.1 M) has

the maximum mass loss rate in AISI 304 specimens at a slope of (-18.0 mg/week), at (0.3 M)

of concentration the slope is (-6.0 mg/week), it rises up again at (0.7 M) (-13.1 mg/week) but

still less than that in the lowest concentration.

Figure 6. The effect of H2SO4 on AISI 316 at different concentrations.

Not unexpected results are shown here; the higher concentration of H2SO4 is the higher

mass loss rate in AISI 316 pieces, as shown from the slopes and the values of mass loss,with

a linear pattern that can be fitted linearly with a high accuracy, which can be evaluated from

R 2.

4.2 THE EFFECTS BASED ON THE STEEL TYPE

The following 6 figures will show us the corrosive effects according to the steel used in

the experiment of this project, 3 figures are for HCl and 3 figures are for H2SO4

Figure 7. The effect of HCl on AISI 304 and AISI 316 at 0.1M.

Figure 8. The effect of HCl on AISI 304 and AISI 316 at 0.3M.

Figure 9. The effect of HCl on AISI 304 and AISI 316 at 0.7M.

We can see clearly from the preceding 3 figures (7, 8 and 9) that is the AISI 316 has a

greater mass loss rate at the 3 different concentrations, which means the AISI 316 has less

corrosion resistance to HCl than the AISI 304, which is expected, the AISI 304 has a greater

chromium contents which helped it to resist the chemical effect of this acid, a third order

polynomial fit is used here in order to reduce the value of R2 as much as possible to have a

good comparison.

.

Figure 10. The effect of H2SO4 on AISI 316 and AISI 304 at 0.1M.

In this low concentration comparison (figure 10) the AISI 316 shows a higher

resistance to H2SO4 at this time, its curve is lying below the curve of AISI 304, Then the AISI

304 has lower resistance to H2SO4 at low concentrations and higher mass loss rate.

Figure 11. The effect of H2SO4 on AISI 316 and AISI 304 at 0.3M.

Figure 12. The effect of H2SO4 on AISI 316 and AISI 304 at 0.7M.

For this two figures (11 and 12) a higher concentrations is used, the AISI 304 again

shows a high corrosion resistance behavior to the H2SO4 acid. For example the slope of AISI

304 curve at 0.7M is (-13.1 mg/week) where it is (-22.8 mg/week) for the other steel type.

4.3 THE EFFECTS BASED ON THE ACID USED

The following two figures (for figure for each steel type) show 6 curves in each, the 3

dashed styles are used to represent the HCl immersed specimens, and the other 3 solid curves

are for representing the H2SO4 immersed ones.

Figure 13. The effect of HCl and H2SO4 on AISI 304.

We can summarize the figure above by, the HCl curves are showing faster corrosion

rates (mass losses) than the H2SO4 curves in AISI 304 specimens, for example if we

approximated the equation of the curve of AISI 304 at 0.1M HCl by omitting the first two

terms which are almost Zero, to have a linear relation, we get a slope of (-76.2 mg/week)

which is greater than the slope of the lower concentration of H2SO4 (maximum mass loss)

which it is (-18.0 mg/week), that’s means the HCl is more corrosive to this steel.

Table 1. Comparison between slopes of the acids curves effecting on AISI 304.

ConcentrationSlope of HCl curve

(mg/week)

Slope of H2SO4 curve

(mg/week)

0.1 M -76.2 -18.0

0.3 M -243.9 -6.0

0.7 M -809.3 -13.1

Figure 14. The effect of HCl and H2SO4 on AISI 316.

As stated in the preceding paragraphs describing the fig. 13, here also we can make the

same description; in other words, the HCl curves of AISI 316 shows rapid growing up (mass

loss) more than the H2SO4 curves did. Also, and by comparing the slopes of the lowest

concentration of HCl and highest one for H2SO4 we make the same conclusion made before.

Table 2. Comparison between slopes of the acids curves effecting on AISI 316.

ConcentrationSlope of HCl curve

(mg/week)

Slope of H2SO4 curve

(mg/week)

0.1 M -25.4 -9.3

0.3 M -92.7 -16.4

0.7 M -399.7 -22.8

Figure 15. The effect of Dead Sea water on AISI 316 and AISI 304.

This figure (fig.15) shows the effect of the Dead Sea water on both types of steels, we

can identify here that the effect of this medium is low compared with the acids effects,

another note here should be added, that the effects on both types is equal somehow, with

more increasing biases to AISI 304 (slope of -4.9 mg/week), as not expected, because it

contains greater chromium contents so it should resist more than AISI 316 (slope of -4.1

mg/week).

5. CONCLUSIONS

The concentration of the acids used is strongly affects the mass loss rate (Figures3, 4,

5 and 6)

The HCl concentration effect: the higher HCl concentration is the higher corrosive

effects on both steel types (Figures 3 and 4)

The H2SO4 concentration effect: in AISI 316 steel, the higher H2SO4 concentration is

the higher mass loss rate, (Figure 6), but in AISI 304 the lowest H2SO4 concentration

is the maximum mass loss rate, (Figure 5).

The HCl has extra corrosive effects on AISI 316 more than AISI 304 at all

concentrations (Figures 7, 8 and 9).

The H2SO4 is more corrosive on AISI 304 at low concentrations (Figure 10), but more

corrosive to AISI 316 at higher ones (Figures 11 and 12).

HCl has more corrosive trends on both steels greater than H2SO4 at all concentrations

(Figures 13 and 14).

The effect of Dead Sea water is very low compared to the acids ones, and it is equal

for both steels with small increase in AISI 304, (Figure 15).

6. RECOMMENDATIONS

Many recommendations can be stated here in order to improve the functionality of this

project, first of all, more concentration may shall use in higher values, the usage of pure acids

is strongly recommended here.

Maybe some heat treatments ought to be done to the steels in order to improve the

surface resistive properties, with more data points the fits will be more descriptive and

helpful for the behavior of the steel at each concentration used.

7. REFERENCES

[1].“Introduction to Engineering Materials”, V. B. John, 4 th edition,

Macmillan. Co..td, 2003.

[2].“Manufacturing Engineering and Technology”, S. Kalpakjian and S. R.

Schmid, 5th edition, Prentice Hall. 2006.

[3]. http://www.cam.ac.com

[4].“An Introduction to Engineering Science and Materials”, D. Callister, Jr.,

7th edition, John Willey & sons. 2006.

[5].“Corrosion resistance of AISI 1018 carbon steel in NaCl solution by

plasma-chemical formation of a barrier layer”, F. J. Depenyou, A. Doubla,

Corrosion Science (2008).

[6]. http://www.wikipedia.com

[7]. http://www.corrosion-doctors.org

[8]. http://www.efunda.com

[9].“Numerical Methods for Engineers”, Steven C. Chapra and Raymond P.

Canale, 2th Edition, John Willey & sons. 1988.

[10]. http://www.engineershandbook.com.

APPENDIX A

LEAST SQUARE METHOD

APPENDIX A: LEAST SQUARE METHOD [8]

When using an mth degree polynomial

to approximate the given set of data,  ,  , ...,  , where  , the

best fitting curve   has the least square error, i.e.,

Please note that  ,  ,  , ..., and   are unknown coefficients while all   and   are

given. To obtain the least square error, the unknown coefficients ,  ,  , ..., and   

must yield zero first derivatives.

Expanding the above equations, we have

The unknown coefficients ,  ,  , ..., and   can hence be obtained by solving the

above linear equations.

APPENDIX B

PROPERTIES OF STAINLESS STEELS AISI 316 AND AISI 304

APPENDIX B: PROPERTIES OF STAINLESS STEES AISI 316 AND AISI 304

PROPERTIES OF STAINLESS STEEL AISI 304:

Table B1.Chemical Composition of AISI 304. [10].

Element C Mn Si Cr Ni P S Mo

Weight % 0.08 2.00 1.00 18.0-20.0 8.0-10.5 0.045 0.03 ---

Table B2.Mechanical Properties of AISI 304. [10].

PropertiesConditions

T (°C) Treatment

Density (×1000 kg/m3) 8 25

Poisson's Ratio 0.27-0.30 25

Elastic Modulus (GPa) 193 25

Tensile Strength (Mpa) 515 

25 hot finished and annealed

(plate, sheet, strip) more

Yield Strength (Mpa) 205 

Elongation (%) 40

Reduction in Area (%) 50

Hardness (HRB) 88 25 

Table B3.Thermal Properties of AISI 304. [10].

PropertiesConditions

T (°C)

Thermal Expansion (10-6/ºC) 17.2  0-100 more

Thermal Conductivity (W/m-K) 16.2  100 more

Specific Heat (J/kg-K) 500  0-100

APPENDIX B: PROPERTIES OF STAINLESS STEES AISI 316 AND AISI 304

Table B4.Electrical Properties of AISI 304. [10].

PropertiesConditions

T (°C)

Electric Resistivity (10-9W-m) 720  25 

PROPERTIES OF STAINLESS STEEL AISI 316:

Table B5.Chemical Composition of AISI 316. [10].

Element C Mn Si Cr Ni P S Mo

Weight % 0.08 2.00 1.00 16.0-18.0 10.0-14.0 0.045 0.03 2.0-3.0

Table B6. Mechanical Properties of AISI 316. [10].

PropertiesConditions

T (°C) Treatment

Density (×1000 kg/m3) 8 25

Poisson's Ratio 0.27-0.30 25

Elastic Modulus (GPa) 193 25

Tensile Strength (Mpa) 515 

25 hot finished and annealed

(wire) more

Yield Strength (Mpa) 205 

Elongation (%) 40

Reduction in Area (%) 50

Hardness (HRB) 95 (max) 25  annealed (plate, sheet, strip)

APPENDIX B: PROPERTIES OF STAINLESS STEES AISI 316 AND AISI 304

Table B7. Thermal Properties of AISI 316. [10].

PropertiesConditions

T (°C)

Thermal Expansion (10-6/ºC) 15.9  0-100 more

Thermal Conductivity (W/m-K) 16.2  100 more

Specific Heat (J/kg-K) 500  0-100

Table B8. Electrical Properties of AISI 316. [10].

PropertiesConditions

T (°C)

Electric Resistivity (10-9W-m) 740  25 

APPENDIX C

PROPERTIES OF HYDROCHLORIC ACID SULFURIC ACID

APPENDIX C: PREPERTIES OF HYDROCHLORIC ACID AND SULFURIC ACID

Table C1. Properties of Hydrochloric Acid. [6].

Hydrochloric acid

IUPAC name Hydrochloric acid

Other names Muriatic acid, Spirit of salt

Identifiers

CAS number [7647-01-0]

RTECS number MW4025000

Properties

Molecular formula

HCl in water (H2O)

Molar mass 36.46 g/mol (HCl)

AppearanceClear colorless to light-yellow liquid

Melting point−26 °C (247 K) 38% solution.

Boiling point 110 °C (383 K), 20.2% solution;,48 °C (321 K), 38% solution.

Solubility in water

Miscible.

Acidity (pKa) −8.0

APPENDIX C: PREPERTIES OF HYDROCHLORIC ACID AND SULFURIC ACID

Table C2. Properties of Sulfuric Acid. [6].

Sulfuric acid

IUPAC name Sulfuric Acid

Other names oil of vitriol

Identifiers

CAS number [7664-93-9]

RTECS number WS5600000

Properties

Molecular formula H2SO4

Molar mass 98.078 g/mol

Appearance clear,colorless,odorless liquid

Density 1.84 g cm−3, liquid

Melting point10 °C, 283 K, 50 °F

Boiling point 290 °C, 563 K, 554 °F (bp of pure acid. 98% solution boils at 338°C)

Solubility in waterfullymiscible(exothermic)