Stress Corrosion Cracking of Brass in Ammonia

Stress Corrosion Cracking of Brass in Ammonia Six samples of brass were taken, stamped to induce residual stress, were then exposed ammonia and ammoniacal copper sulphate solutions of different concentrations and composition for a period of 4 days to study the corrosion characteristics of brass in ammonia. Five samples were immersed in the solution and one of the samples was suspended above solution. On visual examination of the samples revealed some corrosion products with stress corrosion cracking on the surface of brass. Microscopy analysis showed that the non-suspended sample which was exposed to ammonia vapour in presence of moisture and oxygen produced high susceptibility to SCC than immersion samples in aqueous ammonia. The cupric ion present in the solution appears as an oxidant that provides a cathodic reaction and induces stress corrosion cracking of brass in ammonia and ammoniacal solutions. INTRODUCTION: There are three factors under which stress corrosion cracking is possible a) corrosive medium/environment b) material and c) tensile stress. The corrosive medium to induce stress corrosion cracking depends on the potential, pH and temperature. The stress can be applied stress or residual stress. Stress corrosion cracking can occur in lower stress also hence it is the environment which plays a major role. Many studies carried out revealed that failures of brass occur mainly in moist conditions where ammonia, water and oxygen are present. Time of cracking depends on the pH of the solution. Dezincification of copper alloy is possible when the zinc content present is sufficient enough. The aim of this experimental work was to investigate the corrosion behaviour of brass in ammonia. EXPERIMENTAL PROCEDURE: Six brass samples and five test solutions were used in the experiment to study the stress-corrosion cracking of brass. The brass samples were labelled A, B, C, D, E, and F following the residual stress given to them by stamping these letters into their surfaces using drill bits. The stamp was done at one end of the samples while the unstressed part served as the control for the experiment. The solutions serving as the test environments were also labelled using the letters 4A, 4B, 4C, 4D, 4E, 4F and their compositions are shown below. Compositions and colours of test solution observed before immersion Solution Label Composition Colour observed before sample immersion A Ammonium Sulphate with copper (II): 0.5M (NH4)SO4 + 0.05M CuSO4 Pale blue B Ammonia solution with copper (II): 2.5M NH4OH + 0.05M CuSO4 Dark blue C Mattsons solution at pH of 7.2 Medium blue D Modified Mattsons solution containing 5% by volume of 0.1M NaCl Medium blue E 1M Ammonia solution Colourless The labelled samples were placed in the glass jar provided and five of the test samples were filled with enough test solution (10mm) to ensure complete immersion of the sample. Excessive alteration of the concentration of the NH3 solution was avoided by covering the top of the containers. The sixth sample was suspended above solution E (1M NH3 solution) in a glass jar (4F) by means of a surgical nylon string. After sufficient exposure of the samples to the solutions for a period of four days, the samples were removed. The samples were visually examined first upon removal from the test solutions. The colours of the test solutions and corrosion products were recorded before the test samples were cleaned. The test samples were cleaned and rinsed in the pickling solution of 1M sulphuric acid solution in order to remove corrosion products formed on the surface of brass followed by rinsing with deionised water. Finally the samples were dried with tissues before being examined under an optical microscope for stress-corrosion cracking. RESULT AND DISCUSSION: Sample observation after exposure of 4 days to test solutions: Test Label Test Observation from visual examination and optical microscopy Reason 1 Brass sample immersed in solution A Solution remained pale blue. No cracks were seen.corrrosion products found. Localized Corrosion damage at the stressed area observed back of the sample Stress-corrosion cracking may occur with further exposure to the solution. 2 Brass sample immersed in solution B for 4 days Solution was darker compared to the original solution. Brass sample in tarnish condition (dark brown colouration). Crack at the stressed end. Stress-corrosion cracking of the sample. 3 Brass sample immersed in solution C No significant change in solution colour. No cracks were seen.corrrosion products found. Sample shows low possibilities to SCC 4 Brass sample immersed in solution D Dark brown corrosion products. Localized corrosion damage at the stressed end. No cracks seen. Stress-corrosion cracking may occur with further exposure to the solution. 5 Brass sample immersed in solution E Solution changed from colourless to light pale blue. Cracks seen. Colour change is likely due to formation of cupric ion, Cu2+. Stress-corrosion cracking at the stressed end. 6 Brass sample suspended above solution E Solution remained colourless. Tarnish film covering almost the entire surface. Cracks seen at stressed region Stress-corrosion cracking of the sample at the stressed end. Tarnish film likely to be cuprous oxide, Cu2O. Sample A:- A-1 A-2 Fig 1: Sample A immersed for 4 days in solution Ammonium Sulphate with copper (II): 0.5M (NH4)SO4 + 0.05M CuSO4 OBSERVATION: No stress corrosion cracking observed at the stressed end of the sample Fig A-1.some corrosion product was noticed on the back side of the sample Fig A-2. Sample B:- B-1 B-2 Fig 2: Sample B immersed for 4 days in solution Ammonia solution with copper (II): 2.5M NH4OH + 0.05M CuSO4 OBSERVATION: Stress corrosion cracking observed at the stress end and near the unstressed region just near to the stressed end Fig B-1.Dark corrosion product observed on the backside of the sample Fig B-2. Nature of cracks: Intergranular Sample C:- C-1 C-2 Fig 3: Sample C immersed for 4 days in Mattsons solution at pH of 7.2 OBSERVATION: No cracking or any other significant changes observed in this sample after even 4 days of exposure. Only dark corrosion products were observed on the sample. Sample D:- D-1 Fig 4: Sample D immersed for 4 days in Modified Mattsons solution containing 5% by volume of 0.1M NaCl OBSERVATION: No cracking or any other significant changes observed in this sample after even 4 days of exposure. Only dark corrosion products were observed on the sample. Sample E:- Fig: E-1 Fig: E-2 Fig 5: Sample D immersed for 4 days in 1M ammonia solution. OBSERVATION: Stress corrosion cracking observed at the stress end extending to the edges and Dark corrosion product observed on the backside of the sample Fig E-1 and E-2. Nature of cracks: Intergranular Sample F:- Fig: F-1 Fig: F-2 Fig 5: Sample D suspended above in 1M ammonia solution for 4 days. OBSERVATION: Stress corrosion cracking observed at the stress end extending to the edges and Dark corrosion product observed on the backside of the sample Fig F-1 and F-2. Nature of cracks: Intergranular. From Optical microscopy analysis it is evident that sample B (Fig 2 B1B2) immersed in a test solution containing Ammonia solution with copper (II):2.5M NH4OH + 0.05M CuSO4 , Sample E (Fig5-E1E2) suspended above the test solution of 1M Ammonia solution and Sample F (Fig6 F1F2) suspended above the test solution of 1M Ammonia solution had under gone stress corrosion cracking and shows that only in some particular environment SCC occurs. Apart from stress corrosion cracking dark tarnish corrosion product was observed which could possibly be oxide layer of copper. Rest of the three samples A (Fig1 A1 A2) immersed in a test solution containing Ammonium Sulphate with copper (II): 0.5M (NH4)SO4 + 0.05M CuSO4 , C (Fig 3 C1C2) immersed in a test solution of Mattssons solution at pH 7.2 and D (Fig 4 D) immersed in a test solution of Modified Mattsons solution containing 5% by Volume of 0.1M NaCl did not show any cracking but had tarnish corrosion product. These samples suffered localized corrosion at the stressed edges which can be seen in back side of the above 3 samples (Fig A2 C2). The electrochemical reactions of brass in ammonia environment are as follows: Copper free aqueous ammonia is oxygen reduction and primary oxidation reaction is oxidation of copper to form cuprous complex ions. Cu + 2NH3 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ Cu (NH3)2+ + e- The cuprous complex ions formed further reacts with oxygen forming cupric complex ions 2Cu (NH3)2+ + 1/2 O2 + H2O + 4NH3 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ 2Cu (NH3)42+ + 2OHà ¢Ã‹â€ Ã¢â‚¬â„¢ Cuprous complex ion cupric complex ion The formation of cupric complex ions leads to stress corrosion cracking of brass in ammonia solutions. The process does not proceeds indefinitely since the attack of cupric complex ion (oxide layer) occurs at critical copper ion content which leads to decrease in corrosion rate but the cracking continues with the copper ion concentration. It is also evident from the black dark coloured product formed (Tarnish colour) on the surface that the cracks are intergranular in nature.The pores on the surface of the corrosion product were the sites for localized attack, likely to survive at the grain boundaries. In general the stress corrosion cracking in ÃŽÂ ± brass has considered being intergranular. On absence of the black coloured corrosion product it is believed that the cracks to be transgranular nature of crack. CONCLUSION: It is evident from the discussion carried out above that brass is susceptible to stress corrosion cracking in ammonia. Stress corrosion cracking was observed in the regions where residual stresses were generated leaving behind the rest of the areas which were not induced to stress. Formation of cupric complex ions leads to stress corrosion cracking of brass in ammonia solutions. The cracks formed on the brass surface can be further studied under SEM to provide detailed information on the nature of the crack formed. In order to overcome the above problem of stress corrosion cracking the following options can be opted Eliminating any one of the primary factor (Environment, material and stress) will mitigate stress corrosion cracking. Use of more cracking resistance alloys such as Cu-10Ni instead of Cu-Zn

Analysis on “The Merchant of Venice” by William Shakespeare Essay

In life, things are not always what they seem. People may appear to be one way but turn out to be an entirely different. The romantic-comedy, The Merchant of Venice, by William Shakespeare, shows the deliberate use of deception by the characters. Deception is a tool that is used for many purposes. The purposes can be harmful, protective or for personal gain. In The Merchant of Venice, Portia, Jessica, and Shylock are all characters who use deception to carry out their own motives. Shylock, the hated Jew, makes his living through the practice of usury and uses deception when Antonio asks to borrow money from him. Shylock agrees to lend Antonio three hundred ducats if Antonio is willing to sign a bond that would allow Shylock to have â€Å"an equal pound of [his] fair flesh†(I, iii, 145-146). He expresses the bond â€Å"in a merry sport†(I, iii, 141) and uses this bond to also show that â€Å"[he] would be friends with [Antonio], and have [his] love†(I, iii, 134). Though Shylock’s description of the conditions in the bond makes it seem as if Shylock does not mean harm, his intentions are to harm and humiliate Antonio. Antonio says that â€Å"[he] neither lend[s] nor borrow[s] by talking nor by giving of excess†(I, iii, 57-58) and is willing to do that for his dear friend, Bassanio. At first, Antonio is not blinded Shylock’s friendly pretence, aware that Shylock â€Å"is like a villain with a smiling face [and] a goodly apple rotten at the heart†(I, iii, 96-97). However, in the end Antonio accepts the terms of the bond. The cruel use of deception from Shylock is to help fulfill his intention of revenge against Antonio. The deliberate use of cruelness in falsehood is also shown in Shylock’s own daughter, Jessica. Jessica runs off with her Christian lover, Lorenzo. Jessica is â€Å"asham’d to be [her] father’s child†(II, iii, 17) and describes that her â€Å"house is hell†(II, iii, 2). Jessica lies to her father when he asks her what his servant, Launcelot, said to her as he left the house. Launcelot actually told Jessica to watch out for Lorenzo who would be coming by the house later, but she tells her father that Launcelot just said farewell to her. Shylock, of course, trusts his daughter and does not know that she is deceiving him. Another deception by Jessica is when at the night of her elopement, she is disguised as a page boy. She must do this for women  are not allowed to be out in the streets at night during the Elizabethan times. While leaving, she steals and gives Lorenzo some of her father’s valuable possessions. Later on with the jewels she stol e from her father, her mother’s ring is among them and uses it to purchase frivolous things like a monkey. Jessica’s use of deception causes much grief for Shylock not only because of the stolen jewels and ducats but also the loss of his daughter. Portia is another woman who is involved many deceptive plots many which occur during the lottery of the caskets. The choosing of the caskets is bestowed upon her from her father who past away. The lottery involves suitors taking the chance of Portia’s hand in marriage. A particular suitor, the Prince of Morocco arrives to take this risk. In this scene, Morocco pleads Portia to â€Å"mislike [him] not for [his] complexion†(II, i, 1). Portia tells Morocco that she does not mind the complexion of his skin and that he is â€Å"then stood as fair as any corner [she] ha[s] look’d on yet for [her] affection†(II, i, 20). Once he leaves, however, Portia says, â€Å"Let all of his complexion choose me so†(II, vii, 78-79). Portia sets an innocent and admirable face when Morocco or any other suitor is choosing the casket, but the minute he leaves, she mocks them; all except Bassanio. Although this scene shows a cruel deception by Portia, she did it to be polite as was expected of her. Portia uses this deliberate deception further in the play but in a more dignified way. In Act 4 scene 1, Portia dresses as a male lawyer in order to deceive the court and save her husband’s friend, Antonio. She must disguise herself because in Elizabethan times, women were not allowed to participate in law or any other profession. This time, Portia’s deception is not harmful, but is a far more selfless act. Portia sees that disguise is the only method to save Antonio’s life that is very dear to her husband, Bassanio. Dressed as a young lawyer, Portia manipulates the law with her intellect and saves Antonio’s life from certain death by of Shylock. Shakespeare made use of deception and false face in The Merchant of Venice because it is part of our everyday lives. All three characters deliberately use deception in order to achieve their goal. There are many different motivations for the use of a false face and these are shown in The Merchant  of Venice. Whether it is Shylock using it for revenge, Jessica to search for a happier life or Portia to encourage peace, Shakespeare’s use of deception is for the audience to realize that for our own expediency, society takes advantage of the false face.

Essay on Crime

Essay on Crime Inchoate Crimes Inchoate crime is legally defined by the law as a preparedness of an individual to be involved in a crime. Inchoate crimes are sometimes referred to as incomplete crimes since the people intending to commit the crime is stopped by the law from committing the offence before he/she commits the perceived crime. Most of the times inchoate crime often criminals attempt to engage in criminal activity. The laws of several countries describe inchoate crimes as illegally deemed conducts that do not involve an action of an actual harm given that the law serves an obligation of trying to prevent the damage from occurring (Ashworths et al., 454). It is important to note that inchoate crimes involve both direct and indirect actions of crime participation. Inchoate crimes are classified into three parts which include; solicitation, conspiracy and attempt to commit a crime (Utset, 52). Types Of Inchoate Crimes Try To Commit A Crime; An attempt to commit a crime is defined as an inchoate crime since the individuals trying to commit a crime are more often trying to engage themselves in criminal activity to no avail of fulfilling their intended actions. Some examples of attempted crime involve threats and blackmail. Try to get to committing crimes are often precipitated by challenges that individuals go through. Conspiracy is a type of an inchoate crime whereby people come into an agreement with another party in the verge of committing a crime. Conspiracy to commit a crime is an indirect involvement in a criminal activity and therefore referred to as inchoate crime. Persons found guilty to involve in the conspiracy to perform an illegal activity are liable to the wrath of the laws despite the fact that they were not participating in the crime itself. Solicitation, on the other hand, is an inchoate crime whereby a person who intends to commit a crime does not personally engage in a crime but asks another person to commit the offense on their behalf. According to the international standards of legal justice, the person involved in a solicit crime should be charged with a criminal offense even if they do not commit the crime (Van et al., 71). A good example of a solicitation crime is that of murder where an individual pays someone or a group to kill. Defenses That Show That an Actor Did Not Have The Mental Ability To Form The Necessary Intent To Commit A Crime Sometimes individuals may be forced to commit a crime beyond their expectations. Some of the reasons that people often give a defense to committing a crime without their intent include; self-defence, threat, and blackmail or drug influence. People may defend themselves to have committed a crime due to the threat that they receive from perpetrators. For instance, an individual whose loved one has been kidnapped may be involved in a conspiracy crime of failing to report such a case to the police due to threat and blackmail information they received from the criminal. Such individuals due to fear are forced to give into the demands of the major crimes for the sake of their loved one safety. In other instances, people may be involved in non-intended criminal activity when trying to defend themselves from something they perceive to be harmful to their well being. For example, a rape victim who frees his/herself from the perpetrators by use of force and pain infliction to the perpetrator i s considered to have acted in self-defense. However, not all cases of defenses are accepted by the law to be the cause of mental ability to perform an intent crime. For instance; Constitutional requirements do not accept influence of alcohol as a defence to an individual involvelvement in criminal activities ( Sieber, 19). Two Elements Of A Crime The main elements of any criminal acts are illegal act/ actus reus and criminal intent/mens rea. A criminal act described as an individual action to get involved in a criminal act or unlawfully omitting a legal act. Mens Rea, on the other hand, is a criminal element which determines the cause of an individual to engage in a criminal and whether the individual had the right state of mind to justify his/her intent to commit a crime.

Ecologically Sustainable Development and the Role of Australian Court for Workable Solutions Free Essay Example, 2500 words

Chow and Soh, noted the strange shift of primary actors - from local to global and then to corporations. With this, legal and holistic lines are considered. The role of multinational corporations in the environment as well as on the laws enacted to protect it has grown more significant over the decade. The growing importance of MNCs further complicate the problems on environmental laws as policy after policy between local, national, to international communities are forged. As in the case where MNCs invest in one locality, various forms of protections are already in place through bilateral investment treatises, state contracts, as well as governing bodies like the World Trade Organization (WTO). Investors demand more than what exists in one locality in order to protect their stakes and this has been seen to have added to the MNCs power to exploit even the environment (Tienhaara, 2006). As noted earlier, the early 20th century saw states enacting domestic legislation for the environme nt as collective action are needed at the state level. The middle of the century had seen the boom of industrialization so that MNCs actions need to be regulated as the environment becomes advertently affected. We will write a custom essay sample on Ecologically Sustainable Development and the Role of Australian Court for Workable Solutions or any topic specifically for you Only $17.96 $11.86/page MNCs and local corporations became the primary polluters and criminal sanctions were enforced to corporations for violation of pollution control legislation (Reitze, 2001).