Batteries, Fuel cells and corrosion

Different types of Battery and corrosion

by Luis Bello

​​By the end of this section, you will be able to:

​

• Describe the electrochemistry associated with several common batteries

• Distinguish the operation of a fuel cell from that of a battery

• ​Define corrosion

• List some of the methods used to prevent or slow corrosion

​Previous class

• ​Describe the process of electrolysis.

• Compare the operation of electrolytic cells with that of galvanic cells.

• Perform stoichiometric calculations for electrolytic processes.

• ​ Q=I*t (amount of current= Intensity time) Q=nF (moles of e-* 96485 C/s)

Multiple Choice

What is electrolysis?

• breaking down of a compound using a current
• making a compound using a current

Multiple Choice

What is the name of the positive electrode?

• cathode
• anode

Multiple Choice

What is the name of the negative electrode?

• cathode
• anode

Multiple Choice

What is the equation to show what happens to Cl ions at the anode.

• Cl^- --> Cl + e-   
• 2Cl^- --> Cl₂ + 2e-   
• Cl₂ + 2e-   2Cl^- 
• Cl₂ + 2e-  _-->  2Cl^- 

Multiple Choice

What is the product formed at the cathode during the electrolysis of molten magnesium fluoride?

• magnesium
• hydrogen
• fluorine
• oxygen

Multiple Choice

What are the products at the electrodes when dilute sulfuric acid is electrolysed using inert electrodes?

• A

• B

• C

• D

Multiple Choice

The diagram shows the electroplating of a steel object.

A student made the following statements.

1 The object turns a reddish-brown colour.

2 The copper sulfate solution changes to a paler blue colour.

3 The copper electrode becomes smaller.

Which statements are correct?

• 1, 2 and 3

• 1 and 2 only

• 1 and 3 only

• 2 and 3 only

Multiple Choice

What happens when molten NaCI is electrolysed in electrolytic cell?

• Chlorine is produced at positive electrode
• Sodium ions lose electrons at negative electrode
• Electrons flow through liquid from -ve electrode to +ve electrode
• Oxidation occurs at -ve electrode and reduction at +ve electrode

Multiple Choice

Fluorine is manufactured by the electrolysis of HF dissolved in molten KF. A commercial cell for producing fluorine operates at a current of 15.00 A. How many grams of F₂ can be produced per 24 h? (Atomic weight: F = 19.00 g/mol)

2 HF(KF) H₂ (g) + F₂ (g)

a)   131 b)   524 c)   324 d)   255 e)   448

• a

• b

• c

• d

• e

Multiple Choice

How many minutes will it take an electric current of 3.64 A to deposit all the copper from 740 mL of 0.250 M CuSO₄ (aq)? (Atomic weight: Cu = 53.55)

a)  102  b)  208  c)  163   d)  182  e)  144

• a)  102 

• b)  208 

• c)  163 

• d)  182 

• e)  144

​Galvanic

​Rechargeable (Secondary) Batteries

​Fuel Cells: is a galvanic cell that uses traditional combustive fuels, most often hydrogen or methane,

​Corrosion

​Corrosion is usually defined as the degradation of metals by a naturally occurring electrochemical process. The formation of rust on iron, tarnish on silver, and the blue-green patina that develops on copper are all examples of corrosion. The total cost of corrosion remediation in the United States is significant, with estimates in excess of half a trillion dollars a year.

​Protection from corrosion

​Applied coatings: Plating, painting, and the application of enamel are the most common anti-corrosion treatments

​

​​Surface treatments: Small defects can act as an "Achilles' heel", allowing corrosion to penetrate the interior and causing extensive damage even while the outer protective layer remains apparently intact for a period of time.

Biofilm coatings: A new form of protection has been developed by applying certain species of bacterial films to the surface of metals in highly corrosive environments

​​Protection from corrosion

​Sacrificial anode protection: For effective CP, the potential of the steel surface is polarized (pushed) more negative until the metal surface has a uniform potential. With a uniform potential, the driving force for the corrosion reaction is halted.

​Anodization: Aluminium alloys often undergo a surface treatment. Electrochemical conditions in the bath are carefully adjusted so that uniform pores, several nanometers wide, appear in the metal's oxide film. These pores allow the oxide to grow much thicker than passivating conditions would allow. At the end of the treatment, the pores are allowed to seal, forming a harder-than-usual surface layer. If this coating is scratched, normal passivation processes take over to protect the damaged area.