The Effect Of Environment On Corrosion

Project and Seminar Material for Chemical Engineering

The Effect Of Environment On Corrosion


Abstract


In this research project, the various nail were subjected to six environments so as to check the effect of the environments on corrosion of the nails.

Two sets of nails were used; normal nail and concrete nail. Six of each type while the other not coated.

The research was carried out in the physical chemical laboratory of the institute of management and technology.

The environments used are acidic solution, alkaline solution, salt solution, boiled water, air medium and lubricating oil medium, which served as a control medium.

It was observed from the graphs of the weight of metal against time, that acidic environment gave rise to corrosion at a faster rate that other environment. It was also observed that normal nails gave rise to corrosion at a faster rate than concrete nail.

Coating of metals was also concluded to be a method of preventing the rate of corrosion of metals even though it does not stop corrosion.


Table of Contents


  • Title page
  • Certification page
  • Dedication
  • Acknowledgement
  • Abstract
  • Table of content

Chapter One

  • Introduction
  • 1.1 Objectives of the Study
  • 1.2 Scope of the Study
  • 1.3 Significance of the Research

Chapter Two

  • Literature Review
  • Historical Background
  • 2.1 Theory of Corrosion
  • 2.1.1 The Corrosion Process
  • 2.1.2 Energy for the Corrosion Process
  • 2.2 Forms of Corrosion
  • 2.3 Factor Affecting Corrosion Rate
  • 2.3.1 Physical Factors Influencing Corrosion
  • a surface condition.
  • 2.3.2 Environmental Factors
  • 2.4 Corrosion Inhibitors
  • 2.4 Electro Chemical Effects of Corrosion
  • 2.6 Starry Currents
  • 2.7 Corrosion Testing Methods
  • 2.8 Corrosion Monitoring Methods
  • 2.8.1 Coupon Method
  • 2.8.2 Probe Method
  • 2.8.3 Liquid Analysis Method
  • 2.8.4 Corrosion Products Analysis
  • 2.8.5 Gas Analysis
  • 2.9 Protective Coatings

Chapter Three

  • 3.0 Experimental Method
  • 3.1 Materials / Instrument and Tools Used
  • 3.2 Procedure

Chapter Four

  • Experimental Result / Observations

Chapter Five

  • Discussion

Chapter Six

  • Conclusion

Chapter Seven

  • Recommendation
  • References

Chapter One


Introduction

In its broadest sense the term corrosion applied to the destructive alteration of a metal or alloy by chemical reaction with any substance, solid, liquid, or gas. The pattern of attack will be governed largely by the combined influence of several factors relating to the metal or alloy, to the conditions of service, and to the chemical nature of the environment.

  1. The metal may corrode uniformly over its entire surface, as in the resting of iron in the atmosphere.
  2. It may suffer only a superficial attack that does not seriously affect the strength of the metal or alloy but does discolour the surface, as in the tarnishing of silver in the atmosphere.
  3. Corrosion may develop at local areas on an otherwise unattached surface, leading to pitting that may in some instances result in early failure by perforation.
  4. An alloy may be attacked in such a way as to remove one or more of its constituents, leaving a weakened residue of unattached element with poor metallic properties, as in the dezincification of yellow brass or in the graphitization of cast iron.
  5. Excessive corrosion may occur in local area where poor design features tend to aggravate the corrosion conditions, as crevices under rivets, bolts and faying surface.
  6. Use of dissimilar metals sometimes can lead to severe attack of the more active metal where they are joined together.
  7. High tensile stresses plus specific corrosive conditions may result in cracking of a metal because of a corrosion reaction along critical paths in the metal.

In order to provide a quantitative basis for reporting corrosion rates and intensity of attack, the average weight loss of metal per unit area per unit time or the loss in thickness per unit time is usually recorded. Loss in thickness per unit time is more useful in those instances where the engineer is concerned with life of equipment or structure. Average loss is reported in mils per year (MPY) or inches penetration per year (ipy). Where product contamination is vital, the average corrosion rate is expressed in milligrams of metal corroded per square decimeter per day (mdd).

Corrosion process usually occurs because the metal has a tendency to return to its native state, the form in which it is found in nature. This require that the metal atoms relinquish their valence electrons to the environment and because ions in the process. The newly formed ions may then combine with other ions to from compounds. This, when iron corrodes in water, the iron atoms are converted to ferrous ion upon the loss of two electrons.

Fe Fe2++2e-

The ferrous can then combine with hydroxyl ions to from insoluble ferrous hydroxide.

Fe Fe2++20H Fe(0H)

This compound eventually becomes oxidized through content with oxygen the familiar red iron rust, ferric hydroxide. In the electrons from the iron are accepted by oxygen gas molecules and iron oxides are formed.


1.1 Objectives of the Study

The objective of this study in based on the fault that corrosion which has been a major problem in our modern industries has to be prevented and curbed to the barest minimum by putting it environment into consideration in selecting material a structure or piece equipment.


1.2 Scope of the Study

The main metallic material that is being used in this work is nail (iron). This material will be subjected to different medium (environment) viz air medium salt solution medium, distilled water medium acid solution medium, alkaline solution medium and a lubricating oil medium. The observable change brought about by the environment reaction to the material under survey was studied. Iron of varied coatings will also be used.


1.3 Significance of the Research

A complete understanding of corrosion phenomena in all fact requires intensive and prolonged study. However, a general knowledge of the subject can be gained by the engineer through a review or survey of the various ways in which corrosion manifest itself, the factors that govern corrosion process, and the means available to the engineer for controlling or preventing corrosion.

This work will provide a survey that will serve to guide the material engineer his consideration of corrosion behaviour of metals and alloys virus, it will enable those in the oil and gas sector to install pipelines in an environment that will be favourable.


Chapter Five


5.0 Discussion

In order to provide a quantitative basis for reporting corrosion rate and intensity of attack the average weight loss of the metal (nail) in ground per unit time (day) calculated. This was done by plotting the graph of weight of nails (gram per day) and the slope of the graph is the rate of corrosion.(see figures 1a, 1b,2,3,4,5,6, respectively).

In air medium, the slope of the graph was zero (see fig 1a and 16) which mans that the rate of corrosion of normal nail and concrete nails both coated and uncoated was zero. Although, the nails retained their weight but they are losing their luster gradually which means that if exposed in the air for longer time (months or years) may loss weight.

In lubricating oil medium, the slope of the graph was zero (see fig 2a and 26), which means that the rate of corrosion of normal nail and concrete nail both coated and uncoated was zero (grams per day). They metals retain their luster and will not corrode if left for a long time. The lubricating oil medium therefore serves as a control medium.

In boiled water medium, the slope of –0.0667 gramms per day which that the rate of corrosion of the was 0.0667 gramms per day while rate of corrosion of the uncoated normal nail was 0.133 gramms per day. The variation in the rate of corrosion was due to the paint which act as a coat to the nails, which implies that coating help to reduce the rate of corrosion.

Also in the boiled water, medium, the rate of corrosion of uncoated concrete nail was zero while the rate of corrosion of the coated concrete nail was 0.17739 grams per day. The corrosion was due to the weak adherence of the paint to the concrete nail. The concrete nail was observed to be resistant to corrosion in the boiled water environment (see fig 3a and 3b)

In acidic medium, the rate of corrosion of uncoated and coated normal nails are 0.782 grams per day and 0.6875 grams per day respectively which the rate of corrosion of uncoated and coated concrete nail are 0.8grams per day and 0.5909 grams per day respectively (see fig 4a and 4b). It was observed that the rate of corrosion of the uncoated normal nails was higher than that of the uncoated concrete nail due to the special treatment in the formation of concrete nail.

In the alkaline solution environment (see fig 5a and 5b), the rate of slight change in weight of the coated nail was as a result of the weight of the coat (permit). It was observed that colour of the nails were changing gradually, which means that if left in the environment for a longer time may loose weight.

Finally, in the salt solution medium the rate of corrosion for each nail was zero. The nails were gradually loosing their lustres which mean that if left for month or year may loose weight (see fig 6a and 6b).


Chapter Six


6.0 Conclusion

From the research work, the following deduction can be made:

  1. Environment has effect on the rate of corrosion of metals or alloys
  2. Painting of metals helps to prevent the rate of corrosion of metals or alloys to some degree.
  3. Concrete nail has higher resistance to corrosion than normal nails ie treated metal has higher corrosion resistance than untreated metal.
  4. Acidic environment causes higher corrosion rate of metal than other environment.
  5. Prolonged exposure of metal or alloys to any environment may cause determination of the metal or alloys.

Chapter Seven


7.0 Recommendation

Pickling which is one of the best way of complete removal of rust from a metal surface should be used instead of the use of pieces of cloth material as used in this research work before coating.

Also, the handling of most corrosive and acidic chemical should be handled with or by the use of plastic materials.
Pipelines in petrochemical industries should be made of high resistance material. The release of acidic oxides into the environment might cause the formation of acid rain, which can easily corrode the material (pipelines) if not coated with high resistant materials.

Finally, for further research out on this topic-weighing machine that can measure as low as milligrams should be used for effective result.


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