ANODES AND CATHODES

ABSTRACT

Exposure to oxygen causes iron and its alloys to oxidize, or rust. The familiar orange-red color on metal is an indication that metal is slowly reverting back to its natural, lower energy state of ore before the refining process occurred. In this experiment zinc and copper were used. It was revealed that zinc is more active than iron and serves as the anode in the zinc-iron galvanic pair, no blue colouring is present in this case. When using the indicators, zinc ions do not generate a colored compound at the anode. Copper is the least active component in the development of the blue color changes surrounding the nails.

BACKGROUND AND HYPOTHESIS

Metals in manufactured states undergo a process called corrosion that causes them to revert to their initial oxidation states. A reduction-oxidation reaction is a term used to describe the process by which the metal is being oxidized by its surroundings, frequently the oxygen in the air. This reaction is not only electrochemically preferred but also spontaneous. Fundamentally, corrosion is the development of voltaic, or galvanic, cells in which the target metal serves as an anode and typically deteriorates or loses functional stability. This refers to the electrochemical oxidation of metal in reaction with an oxidant, such as oxygen or sulfur, in its most widespread usage. Rusting is a well-known instance of electrochemical corrosion and is the development of iron oxides. This kind of deterioration often produces oxides or salts of the parent metal and gives the material a distinctive orange color. Along with metals, materials like ceramics and polymers can also experience corrosion, albeit in these cases the term “degradation” is more suitable. The beneficial characteristics of materials and structures, such as strength, appearance, and permeability to liquids and gases, are compromised by corrosion. The corrosion process can be significantly impacted by exposure to certain substances, but many structural alloys corrode simply from exposure to moisture in the air. It is possible for corrosion to concentrate locally to form a pit or fracture or it might disperse across a large region relatively evenly to corrode the surface. Corrosion happens on exposed surfaces because it is a diffusion-controlled process. Therefore, techniques for reducing the activity of the exposed surface, such chromate conversion and passivation, can enhance a material’s resistance to corrosion.

Hypothesis:

1. To test for corrosion on various metals and learn how corrosion happens.

• Anodes and cathodes are found in relation in relation to corrosion processes.

• Corrosion can be defended effectively

PROCEDURES

1. A 500 ml beaker containing 200 mL of 0.1M sodium nitrate was heated to boiling. 3 g of powdered agar were added while being stirred with a glass rod. The mixture was heated while being swirled to dissolve the agar.

• To the agar suspension, 10 drops each of 0.1M potassium ferricyanide and phenolphlthalein were added. The mixture was well mixed.

• Iron nails were used to clean three iron nails.

• The bottom of the first petri dish was covered with a single iron nail.

• Steel was used to polish 10 cm each of copper and zinc wire.

• The second iron nail was encased in a thin layer of 10 cm copper wire. The third iron nail was thinly encased with 10 cm zinc.

• The second petri dish’s bottom was filled with the second and third wrapped iron nails. The iron nails were separated from one another so as to prevent them from coming into contact.

• Iron nails were placed in both petri dishes and covered with warm agar to a depth of about 1 mm.

• For roughly 48 hours, both dishes were covered and let to stand.

1. On the first day, the successive color changes over the course of several hours were seen.

1. On day 2, the petri dishes were viewed and the results were noted using both a white and a black background.

DISCUSSION

The goals of this experiment are to clarify the causes of corrosion, the roles played by anodes and cathodes during the corrosion process, and to show how to effectively prevent corrosion. The cathode reaction involves the flow of electrons from the anode through the metal to the cathode, where they can mix with positively charged ions.

Corrosive attacks can take many different forms, and different metals are impacted to varying degrees. Attacks could take the form of overall rusting or tarnishing with sporadic perforations in particularly damaged locations. Near the intersection of two different metals is where corrosion may form more frequently. Pitting could cause a highly localized attack on the metal. A metal’s strength can be destroyed by corrosion-induced cracking. These examples of rusting in action are all too common. With the substances that can induce corrosion at times, corrosion may also be limited to the wrapper side.

Zinc is utilized to partially plate the nail. Over several hours, color development is observed. Because zinc is more active than iron and serves as the anode in the zinc-iron galvanic pair, no blue colouring is present in this case. When using the indicators, zinc ions do not generate a colored compound at the anode. As a result, the zinc region does not become colored. The iron surface begins to turn red, indicating that it is now only functioning as a cathode. The secondary oxygen concentration cell impact on the zinc is what causes any localized red coloring that may appear as the zinc strip emerges from the gel. This must be separated from the zinc-iron nail galvanic couple’s reactions.

Because it can react with the nails itself, copper is the least active component in the development of the blue color changes surrounding the nails. After many hours, the copper surface begins to take on a brown hue, and the unwrapped side begins to take on a blue hue. Additionally, the wrapped portion of the nails starts to turn pink.

CONCLUSION

The experiment’s goals, which included determining how corrosion occurs, where anodes and cathodes are found during the corrosion process, and how to prevent corrosion effectively, were all met.

REFERENCES

Lab Manual CMT 555.  Electrochemistry and     Corrosion Science.

The Royal Society of Chemistry, Jan 2016, https://eic.rsc.org/exhibition-chemistry/nailing-corrosion-demonstrations/2000054.article

WordPress, October 2012. Galvanic Corrosion of Iron Nail. https://tgreen230493.wordpress.com/2014/10/30/galvanic-corrosion-of-an-iron-nail/