Lat oratory Date Section Experiment 10-Post-Laboratory Questions 1. Although Fig

Question

Lat oratory Date Section Experiment 10-Post-Laboratory Questions 1. Although Fig. 1 indicates that chromium (C) is more active than iron (Fe), chrome plating is nevertheless a very effective procedure to prevent the corrosion (i.e., oxidation) of iron. Provide an explanation for a layer of chrome being able to protect iron despite being a more active metal 2. Galvanization is a process of protecting iron from corrosion by coating the metal with a layer of zinc. Although Zn is more active than Fe, zn reacts with atmospheric gases to form zinc carbonate (ZnCO), a hard, durable substance which shields the remaining Zn and the underlying Fe. Suggest a series of reactions involving common atmospheric gases which could converted Zn into ZnCO3. 3. If the zncoazn coating of galvanized iron broken and the underlying iron begins to corrode (i.e., oxidize), a chemical reaction intervenes and the corrosion products back to iron. Suggest a reaction which could account for this chemical protection of the iron

Explanation / Answer

1.Chromiumplating or chrome or passivation is effective when made prior to paintings.It improves adhesion of paint particles and prevents the surface for following applications to enhanced corrosion protection.Passivation traetment eliminates which is coming with water rinsing or after zinc/iron phosphate coatings.

2. Zinc + Oxygen ---> Zinc oxide (unstable)

Zinc + Moisture ---> Zinc Hydroxide (unstable)

Zn+ O2 + CO2 --- > ZnCO3 ----->Zinc Carbonate(Stable and protective barrier)

3.Zinc is more reactive than iron and it oxidises before iron.Even if the zinc is just in a large block and iron is fully exposed,it will still oxidise first ,this is how sacrifical protection works.

If a scratch penetrates zinc film,the iron is still protected because of zinc oxidizes preferntially:

Fe2+ + 2e- ----->Fe E0= -0.447 V

Zn2+ +  2e- ----->Zn E0= -0.761 V

4.Sodium metal is part of alkali metal group and it is highly reactive in nature and is never found in pure state in nature.It is easily tarnished and has a low melting point and thus is stored in oil or paraffin wax.It is chemically found combined with chloride.

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