The best comparison between Metal plating and Electroplating Chemistry [#1]

Electroplating chemistry is one of the oldest techniques used for metal plating chemistry and metal finishing. The electroplating experiment starts with the electrochemical deposition of metal on the targeting surface. Most of the electroplating experiment fundamentals come from Faraday’s law. How to use them for science experiments? How to do a modern electroplating experiment? The following aspects are important for electroplating chemistry.

Electrode potential between the electrodes
Kinetics and mechanism of electrodeposition on the surface
Growth mechanism of electrodeposition
Electroless and displacement depositions as free deposition

The best comparison between Metal plating and Electroplating Chemistry [#1]

Photo by Pierre Châtel-Innocenti on Unsplash

Table of Contents

Fundamental of Metal plating and Electroplating Chemistry:

Here, we are going to discuss the fundamental laws on electrodeposition. These rules and theories are very important before going to do any science experiments.

How electro potential comes in the electrode?

The generation electro potential is from the interaction and interexchange between metal and their metal ions interfaces. Let me explain in little more detail, Metal ions are deficient of an electron. But the Metal electrode is rich in the electrode. If the metal electrode is immersed in the same metal ion solution, then interexchange and interaction take place between the metal electrode and metal ions.

In addition, some metal ions from the solution enter into the solid crystal lattice and some metal from the solid crystal lattice moves into the solution as metal ions. This entire process depends on the pH scale of the solution. Any have these pH scale characteristics we will discuss later. For time being we keep the pH aside.

If the electrode is rich with negative charges, then metal ions move towards the electrode and deposit as a metal on the surface of the electrode. This type of electrode is called the cathode. Similarly, if the electrode is deficient in charge, then metal from the solid crystal lattice electrode moves as metal ions towards the solution with the anion species in the solution. In this situation, anion species move towards the anode and at the same time, metal ions come from the solid crystal lattice of the metal electrode. This type of electrode is called the anode. In simple, the Cation moves toward the cathode, and the anion move toward the anode.

Photo by Robert Zunikoff on Unsplash

What is Faraday’s Law?

Sir Michael Faraday was a British scientist. He worked in a variety of different fields of chemistry and physics. Moreover, the Royal Society of Chemistry (RSC) honored his name to its journal the Faraday Discussion. Faraday’s law states that the amount of electrochemical deposition reaction that occurs on an electrode is directly proportional to the amount of electric charge ‘Q’ passed through an electrochemical cell between the two electrodes. Thus, The weight of a deposition product of electrolysis or electroplating chemistry is ‘we, then Faraday’s law states as follows

                                    W = ZQ

Here ‘Z’ is the electrochemical deposition reaction equivalent, this is the constant proportionality for electrochemical reaction. Then charge ‘Q‘ is the product of the current flow ‘I ‘ in the unit of amperes (A) and the overpass time duration of ‘t’ in seconds,

                                        Q=It

According to Faraday’s law, the production of one gram equivalent of a deposition product on the electrode as an outcome of an electroplating chemistry experiment, Wₑ𝚚, in an electrochemical cell requires 96,487 C. The constant 96,487 is termed the Faraday constant ‘F’. The coulomb charge (C) is the quantity of electricity transported by the flow of one ampere current flow for one second time duration. This understanding of Faraday’s law is required for science experiments.

How to measure current efficiency in electroplating?

When two or more electrochemical reactions occur simultaneously on the surface of an electrode, the number of coulombs charge of electricity passed depends on the summation of the number of equivalents of each electrochemical reaction. For example, during deposition of copper Cu from the copper ion solution of copper sulfate in dilute sulphuric acid, two types of cathodic reactions occur the deposition of Cu (the reduction of copper ions) and the reduction of hydrogen ions into hydrogen gas.

The current efficiency CE of the j th electrochemical process, namely of any one of the simultaneous electrochemical reactions is defined as the number of coulombs charge required for that electrochemical reaction, Qj, divided by the total number of coulombs the charge of current passed, Qtotal. An alternative way to find current efficiency CE is by using the weight deposition of the electrochemical reaction of electroplating. Thus, wj is the weight of metal j actually electrodeposited and wtotal is that which would have been electrodeposited if all the current had been used for electrodepositing metal j.

Photo by Chris Yates on Unsplash

How to measure the thickness of coating surface on metal by electroplating?

The deposit thickness can be calculated by considering the volume of the electroplating deposit on the metal surface. Since the volume of the electroplating deposit ‘V’ is the product of the electroplating surface area ‘a’ and the electroplating thickness (height) ‘h‘, it gives h=(V/a). The volume of the electroplating deposit is related to the weight of the deposit ‘w’ and the density of the deposit ‘d’ by the relationship defining the density,d=(w/V) Thus gives h=(w/ad).
The electroplating chemistry mainly depends on electrodeposition time duration. This is the main factor that affects the electroplating thickness. If we apply at a given current density in ampere, we introduce Faraday’s law as follow

                   h = (ZQ/ad)                                             

                          h= (ZIt/ad)

If we rearrange the above equation, we get time in seconds,
 
                                                                                                   t=(had/ZI)

This final equation plays a very critical role in any electroplating chemistry science experiments. If you want any desired thickness of electroplating for a particular metal surface, then you need to supply that specific current for a fixed time duration. This electroplating chemistry concept, we use in our upcoming science fair projects. For more information and updates on the science project, please check our homepage.