Department Of Biology Faculty of Science and Mathematics

SBI 3013 Information amd Communication Technology in Biology PROJECT REPORT

DATA LOGGER-CORROSION EXPERIMENT GROUP : B

Lecturer’s : Encik Azmi Bin Ibrahim By :

Nazihan Binti Nazali Ika Priska Wahyuni Binti Dasmir Nurul Ain Safirah Binti Mohd Khiri

D20162075559 D20162075570 D20162075558

ENGAGED Corrosion is a natural process, which converts a refined metal to a more chemicallystable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and stopping corrosion. In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfur. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide or salt of the original metal, and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases. A corrosion inhibitor is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy. The effectiveness of a corrosion inhibitor depends on fluid composition, quantity of water, and flow regime. A common mechanism for inhibiting corrosion involves formation of a coating, often a passivation layer, which prevents access of the corrosive substance to the metal. Permanent treatments such as chrome plating are not generally considered inhibitors, however. Instead corrosion inhibitors are additives to the fluids that surround the metal or related object. DC Electrochemical techniques have been used over most of this period to rapidly acquire corrosion data in actual plant environments and bench scale laboratory tests. More recently AC electrochemical tests have been included to evaluate non-metallic coatings for their corrosion protection ability. The ability to acquire live time corrosion data under process conditions has enabled us to identify the specific point in batch reactions in which stress corrosion cracking is occurring. Very brief but very severe cracking has been identified in start-up conditions with these tests. This knowledge has enabled operators to modify start up conditions and either save the reactors or extend their life. The approach is briefly outlined below: a. A sample of the alloy has its potential relative to a reference electrode changed continuously or scanned from a negative or cathodic voltage to a positive or anodic voltage in the solution of interest at different stages of the reaction. The current (corrosion rate) and voltage are recorded. This can be done in a highly controlled laboratory set up or in real world conditions. (Metallurgical Consulting currently use a Gamry Ref 600 system.) The results are plotted as shown in the graph below. b. Stress Corrosion Cracking (SCC) in active-passive metals such as stainless steels is known to occur under specific electrochemical conditions as shown in the graph. c. The nature of the resulting current vs voltage plot and where the metal potential lies provides the data needed in order to determine when the cracking occurs.

The size and location of the passive region is affected by many variables including solution composition, pH, and temperature. Handbook corrosion tables cannot cover all of the issues for plant applications. However, DC potentiodynamic corrosion testing can provide data on the nature of the corrosion conditions for specific situations. Instances have been observed where stainless reactors started out in the active region and then went passive. They must cross through a region of SCC in order to do this. Adjusting start up conditions to allow the system to start up in the passive region has reduced or eliminated the cracking. Pitting can be addressed by potentiodynamically scanning the specimen into the transpassive region and then reversing the scan. Pitting conditions will cause the reverse current to stay high. The extent of the return hysteresis will say much about the pitting conditions. This type of test was used with side loop specimens on a once through river water heat exchanger to monitor the performance of ferrous sulfate additions to inhibit pitting corrosion. See paper. (PDF - 5.12MB) Corrosion rates can also be measured electrochemically since the current density is directly related to corrosion rate by Faraday's law. The corrosion rate on stainless steels should be very low in the passive regions. However, rates as high as 5.0 inch per year have been measured in the active region. These rates persisted for a short time during start up only but when all startups were totaled, the total wall loss estimated from corrosion data came close to the actual measured wall loss.

Corrosion Inhibitor: A chemical substance which when added to an environment is small concentration, effectively to prevent corrosion of a metal. inhibitors recommended to protect metallic materials, especially ferrous metals and alloys, from corrosion. The uses: To inhibit the corrosion process of metal.A corrosion inhibitor is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy.

Natural corrosion inhibitor: All organic compounds especially those with N, S and O showed inhibition efficiency. But, most of these compounds are expensive and also toxic to living beings.Plant extracts also rich sources of ingredients which have very high inhibition efficiency. Another resources of corrosion inhibitor  l-ascorbic acid  quantum chemical methods  2,5-bis(4-methoxyphenyl)-1,3,4-oxadiazole  2-hydrazino-6-methyl-benzothiazole  Caffeic acid  polydentate Schiff base compounds (PSCs)

EMPOWER Definition - What does Potentiodynamic mean?

RE=reference electrode CE=counter electrode WE=wall electrode  The reference electrode (RE) is used to monitor and maintain potential at the WE surface. 

Current is passed through the electrolyte between the counter electrode (CE) and the WE with a low resistance connection provided and monitored by the potentiostat.

 Evaluation of the current/potential behavior under a variety of conditions leads to the understanding of a range of corrosion phenomena.

Potentiodynamic is a term describing the measured change in the electrical potential (voltage) of a system. In electrochemistry, this term is used in describing polarization methods in the corrosion industry. Potentiodynamic refers to a polarization technique in which the potential of the electrode is varied over a relatively large potential domain at a selected rate by the application of a current through the electrolyte. Potentiodynamic polarization is often used for laboratory corrosion testing. It can provide significant useful information regarding corrosion mechanisms, corrosion rate and susceptibility of specific materials to corrosion in designated environments. Potentiodynamic is also known as potentiodynamic polarization. Potentiodynamic polarization is a technique where the potential of the electrode is varied at a selected rate by application of a current through the electrolyte. This technique is used in polarization of specimens for corrosion testing. A potentiodynamic polarization variant is cyclic voltammetry, which involves sweeping the potential in a positive direction until a predetermined value of current or potential is reached. Then the scan is reversed toward more negative values until the original value of potential is reached. Another variation of potentiodynamic polarization is the potentiostaircase method, which is a technique for polarizing an electrode in a series of potential steps where the time spent at each potential is constant, while the current is often allowed to stabilize prior to changing the potential to the next step. The step increase may be small, in which case, the technique resembles a potentiodynamic curve. Electrochemical potentiodynamic reactivation (EPR) is a polarization method that evaluates the degree of sensitization of stainless steels. This method uses a potentiodynamic sweep over a range of potentials from passive to active (called reactivation). The most popular variant is the cyclic polarization test. This test is often used to evaluate the pitting susceptibility of a material. The potential is swept in a single cycle or slightly less than one cycle, usually starting the scan at the corrosion potential. This technique has been especially useful to assess localized corrosion for passivating alloys such as S31600 stainless steel, and other alloys such as titanium and zirconium. Though the generation of the polarization scan is simple, its interpretation can be difficult.

RESULT

Fig: Corrosion cell

Metal surface after corrosion

Example result:

Trial

Surface area (𝒄𝒎𝟑 )

Average pH before testing

2 3 4 5 6 AVERAGE

1.844 1.924 1.863 1.963 1.860 1.891

7.19 7.20 7.20 7.18 7.19 7.19

Average Final pH after open testing circuit 𝑬𝒓 (mV vs SCE) 7.20 -193 7.22 -185 7.21 -187 7.19 -186 7.19 -188 7.20 -188

Corrosion Breakdown 𝑬𝒓 rate potential − 𝑬𝒃 𝒃 (mpy) 𝑬 ( mV vs (mV SCE) vs SCE) 0.026 0.025 0.023 0.024 0.024 0.025

288 336 284 388 325 324

481 521 471 574 513 521

ENHANCES OF NATURAL INHIBITOR TO CORROSION The use of inhibitors for the control of corrosion of metals and alloys which are in contact with aggressive environment is an accepted practice. Large numbers of organic compounds were studied and are being studied to investigate their corrosion inhibition potential. All these studies reveal that organic compounds especially those with N, S and O showed significant inhibition efficiency. But, unfortunately most of these compounds are not only expensive but also toxic to living beings. It is needless to point out the importance of cheap, safe inhibitors of corrosion. Plant extracts have become important as an environmentally acceptable, readily available and renewable source for wide range of inhibitors. They are the rich sources of ingredients which have very high inhibition efficiency. This article gives a vivid account of natural products which are used as corrosion inhibitors for various metal and alloys in aggressive media. Corrosion control of metals is technically, economically, environmentally, and aesthetically important. Corrosion of metals is the major problem in industries. Considering environmental and ecological reasons, green inhibitors are found to be effective. As organic corrosion inhibitors are toxic in nature, so green inhibitors which are biodegradable, without any heavy metals and other toxic compounds, are promoted. Also plant products are inexpensive, renewable, and readily available. Inhibition efficiency depends on temperature and concentration of inhibitor. Some of the inhibitors are mixed-type inhibitors. From the economic and environmental view points, plant extracts are an excellent alternative as inhibitors because of their availability and biodegradability. These extracts can be obtained in a simple way and purification methods are not required. The extracts are generally obtained from cheap solvents that are widely available, at a low cost and with low toxicity; the aqueous extract is more relieved, but due to the low solubility of many natural products in water, common ethanol extracts are also obtained. These extracts contain a variety of natural products such as essential oils, tannins, pigments, steroids, terpenes, flavones and flavonoids, among other well-known active substances used as CIs. In general, these compounds present conjugated aromatic structures, long aliphatic chains such as nitrogen, sulfur, and oxygen

heteroatoms with free electron pairs that are available to form bonds with the metal surface; in most cases, they act synergistically to exhibit good efficiency regarding the corrosion protection. This can be demonstrated in the case of Ginkgo biloba in which the main components (flavonoids and terpenoids) have been identified Over the years, considerable efforts have been deployed to find suitable corrosion inhibitors of organic origin in various corrosive media .In acid media, nitrogen-base materials and their derivatives, sulphur-containing compounds, aldehydes, thioaldehydes, acetylenic compounds, and various alkaloids, for example, papaverine, strychnine, quinine, and nicotine are used as inhibitors. In neutral media, benzoate, nitrite, chromate, and phosphate act as good inhibitors. Inhibitors decrease or prevent the reaction of the metal with the media. They reduce the corrosion rate by adsorption of ions/molecules onto metal surface, increasing or decreasing the anodic and/or cathodic reaction, decreasing the diffusion rate for reactants to the surface of the metal, decreasing the electrical resistance of the metal surface inhibitors that are often easy to apply and have in situ application advantage.Several factors including cost and amount, easy availability and most important safety to environment and its species need to be considered when choosing an inhibitor. Corrosion remedies to decrease pollution which is human health, animals and vegetal life or various materials, for example, metals and nonmetals, are at risk due to the hazardous nature of many organic and inorganic pollutants. Hazards may occur naturally or as a result of human activities (such as industrial pollution, transportation accidents and damage, radioactive pollution, water pollution, petroleum pollution, etc). Corrosion is considered one of these causes .The use of some environmentally unacceptable materials such as chromium salts has been restricted because chromium (Cr+6) is highly toxic and carcinogenic, and been replaced with environmentally friendly compounds for alloy coatings. Strontium chromate, zinc chromate, and chrome phosphate, etc are heavy-metal-based and largely carcinogenic. Lead-based coatings cause health complications in children. Small amounts of chromic acid or potassium dichromate can cause kidney failure, liver damage and blood disorders. Chromate mists entering the lungs may eventually cause lung cancer .Chemical pickling of materials such as stainless steel (SS) by using HF−HNO3 mixture.Results in the disadvantage of generation of nitrous gas emissions and nitrate effluents, which pollute the environment. HCl has proved to be more economical and efficient in the pickling of metals, acidization of oil wells and in cleaning scales, compared to other mineral acids. The great advantage of HCl over other acids in cleaning and pickling operations lies in its ability to form metal chlorides, which are extremely soluble in aqueous phase, compared to sulfate, nitrate and phosphate.

CONCLUSION Inhibitors are a great method of preventing corrosion and are easy to apply. Has application in a wide range of. Potentiodynamic polarization techniques were mainly used to confirm corrosion inhibition mainly in sulphuric acid or hydrochloric acid media. A lot of potential is still untapped especially computational modelling of the major extract components on mild

steel. This will help in establishing detailed mechanisms for corrosion inhibition. Work on the studies of real industrial effluent or real life situations is limited. There is need for further work on the exploration of these plant materials in other corrosive environments such as carbon dioxide, sulphur dioxide, and hydrogen sulfide. Further research should also be focused on the extraction and structural elucidation of active plants extracts to ascertain the structure of these compounds so as to help understand the process of corrosion inhibition. Scale-up experiments for industrial applications also need to be done so as to commercialize these natural extracts to effectively replace the conventional chemicals currently used to control corrosion.

EXTENSION • • • • • • •

Welding Fracture mechanics testing Metallurgy Materials science Stress analysis Fatique analysis Strain gauge testing

REFERENCES 1. What is Potentiodynamic? - Definition from Corrosionpedia. (n.d.). Retrieved March 16, 2017, from https://www.corrosionpedia.com/definition/911/potentiodynamic

2. Metal alloy surface after corrosion - Google Search. (n.d.). Retrieved March 16, 2017, from https://www.google.com/search?q=metal%2Balloy%2Bsurface%2Bafter%2Bcorrosio n&espv=2&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiR_uG7ntvSAhUDtpQK HRXIAoIQ_AUIBigB&biw=1366&bih=662#imgrc=wZyPOI98LPjsIM: