What is Patination?

The process in which a piece of metal develops it's metal oxide coating intentionally or naturally is called Patination. The oxide layer is usually termed as Patina.

References: http://www.pbs.org/wgbh/roadshow/fts/lasvegas_200706A35.html

What is Dislocation of Metals?

When the atoms are out of the original position (dislocated) inside the crystal structure, the phenomena is called Dislocations of Metals. It is likely to be happened when a stress is applied on metals' crystal structure. This is a linear defect. There are mainly two types of Dislocation of Metals.
1. Edge Dislocation
2. Screw Dislocations
Dislocation of Metals is hindered by grain boundaries.

References: https://www.nde-ed.org/EducationResources/CommunityCollege/Materials/Structure/linear_defects.htm
http://resources.schoolscience.co.uk/Corus/16plus/steelch1pg5.html

What is Stacking Fault?

In crystallography, the defect that denotes the disordering of crystallographic planes is called Stacking Fault. It occurs mainly in closed packed crystal structure. Stacking Faults by themselves are two-dimensional. It is a planar defect.

References: http://www.tf.uni-kiel.de/matwis/amat/def_en/kap_5/backbone/r5_4_1.html
                      http://iopscience.iop.org/article/10.1088/0034-4885/33/1/307/pdf

What is Watt's solution?

Nickel Sulphate, Nickel Chloride and Boric acid combines Watt's bath. Nickel Sulphate provides the right concentration of Ni ions. Nickel Chloride help in corrosion of the anode. Boric acid acts like a pH controller of the electrolyte.

What is an amphoteric substance?

The substance which can act like both acid and base while reacting with other substances. It is like a double agent! The word ampho comes from greek 'amphi' which means 'both'.

What is Divergence?

The mathematical term that denotes the amount of flux leaving or entering a point is called divergence. Hence, divergence represents the volume density of moving flux from an infinitesimal source. It is a scalar product.

The value of the divergence of a vector is positive when the vector field points outward from the region (point of location).

The following equation shows the divergence (∇•) of  an electric potential field.
∇• (k∇u)=0

References: http://mathinsight.org/divergence_idea

What is Gradient?

The gradient is the rate at which the line rises (or falls) vertically for every unit across to the right. So the gradient of a line is determined by the ratio of vertical change to horizontal change. Hence,

Gradient =  Change in Y direction Change in X direction The gradient of a straight line shows how steep the line is.

What is the equation for temperature dependence of the conductivity of electrolyte?

As the temperature of the electrolyte increases, the conductivity of the electrolyte also increases, and this in turn affects the kinetics of the anodic dissolution process. The change in the electrolyte conductivity is given by:
K = K0[l + AT. ©]

where: © = T — T0 is the increase in temperature, and AT is the temperature coefficient of conductivity at the initial temperature T0, at the nozzle outlet.

Source: Study of Electrochemical Jet Machining Process by J. Kozak, K. P. Rajurkar & R. Balkrishna, University of Nebraska, November 1996, Page 3.

What is Current Density?

Current Density is the amount of electric current flowing per unit of cross-sectional area of a material. 
Usually Current Density is denoted by J.

What is Ohm's Law?

Ohm's Law:
The potential difference across an ideal conductor is proportional to the current through passing through it.
   where I = Electric Current, V = Potential Difference (Voltage), R = Resistance.

A generalization of this law is given below.
  where J = Current density, σ = Conductivity, E = Electric field

What is Faraday's Law in Electrochemistry?

Faraday's law:


'The amount of any substance deposited or dissolved during electrolysis is proportional to the quantity of electric charge passed through and to the equivalent weight of the substance to be deposited or dissolved'


  Where m=mass of substance deposited or dissolved
                                    Q = total electric charge passed through
                                    F = Faraday's constant = 96485 C mol⁻¹
                                                            M = Molar mass of the substance
                                    Z = Valency number  

Further, Q=It; where I= Electric Current, t=total time of electrolysis



Note that The equivalent weight of a substance is actually equal to its molar mass (M) divided by the change in oxidation state it undergoes upon electrolysis process. It is usually equal to its charge or valence.

What is Non-polarizable Electrode?

If the potential of an electrode does not change with the variation of current passing through it, is called a Non-polarizable Electrode.