Industrial Chemistry - Electroplating

Industrial Chemistry - Electroplating
History

In 1805, modern electrochemistry was invented by Italian chemist Luigi Valentino Brugnatelli.

In 1839, scientists in Britain and Russia had independently devised metal deposition processes similar to Brugnatelli's for the copper electroplating of printing press plates.

In the late 19 th century, the plating industry received a big boost with the advent of the development of electric generators in.

Definition

The process of applying metal coating on metallic or non metallic surface through electrochemical process.

A process that uses electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode.

Types of Electroplating

Mass Plating

The parts to be plated are kept in barrels which are tumbling while remaining immersed in the metal solution to be plated.

Rack Platting

The parts to be plated are hung on the racks which are immersed in the metal solution which is to be coated.

Continuous plating

Used to provide uniform and smooth coatings to wires, tubes and stripes. The parts to be coated or plated are moved continuously through plating sequence.

Line plating

A technique in which the parts to be coated are moved in production line.

Function
  • Appearance
  • Protection from corrosion
  • Engineering or mechanical properties
  • Special surface properties
Application
  • Decorative purposes
  • Protection against atmospheric conditions
  • Electrical conductivity
  • Industrial applications (automobile, airplanes, electronics, jewelry, and toys).
Theory Process

Industrial Process

Strike
  • A strike uses a high current density and a bath with a low ion concentration. The process is slow, so more efficient plating processes are used once the desired strike thickness is obtained.
  • If it is desirable to plate one type of deposit onto a metal to improve corrosion resistance but this metal has inherently poor adhesion to the substrate, a strike can be first deposited that is compatible with both. 
Electrochemical Deposition

Advantages :
  • The thickness and morphology of the nano structure can be precisely controlled by adjusting the electro chemical parameters;
  • Relatively uniform and compact deposits can be synthesized in template-based structures;
  • Higher deposition rates are obtained;
  • The equipment is inexpensive due to the non-requirements of either a high vacuum or a high reaction temperature.
Pulse Electroplating (PED)
  • A process involves the swift alternating of the potential or current between two different values resulting in a series of pulses of equal amplitude, duration and polarity, separated by zero current.
  • By changing the pulse amplitude and width, it is possible to change the deposited film's composition and thickness.
Brush Electroplating
  • The brush, typically a stainless steel body wrapped with a cloth material that both holds the plating solution and prevents direct contact with the item being plated, is connected to the positive side of a low voltage direct-current power source, and the item to be plated connected to the negative.
  • The operator dips the brush in plating solution then applies it to the item, moving the brush continually to get an even distribution of the plating material.
Electroless Deposition
  • An electroless deposition process uses only one electrode and no external source of electric current.
  • However, the solution for the electroless process needs to contain a reducing agent so that the electrode.
Cleanliness
  • Cleaning processes include solvent cleaning, hot alkaline detergent cleaning, electro-cleaning, and acid treatment etc.
  • The most common industrial test for cleanliness is the waterbreak test, in which the surface is thoroughly rinsed and held vertical.
  • The electroplating process can displace these easily since the solutions are water-based. Surfactants such as soap reduce the sensitivity of the test and must be thoroughly rinsed off.
Waste Treatment
  • Plating wastewater contains heavy metals, oil and grease and suspended solids at levels that might be considered hazardous to the environment and could pose risks to public health.
  • The high toxicity and corrosiveness of plating waste streams, plating facilities are required to pretreat wastewater prior to discharge in accordance with National Pollutant Discharge Elimination System (NPDES) permits as required by the Clean Water Act (CWA).
1. Precipitation and Coagulation

pH is raised from ~3 to 8.5 with the pH controller using caustic while adding a coagulant such as ferric chloride. 

2. Flash Mix

The wastewater with it’s precipitated pin floc is introduced to the flash mix zone where a polymer flocculent is added.

This stage maximizes flocculent dispersion throughout the coagulated wastewater.

3. Flocculation

The wastewater is now introduced to the slow mix zone to agglomerate the pin floc into larger rapid settling particles.

Summary

Purpose: Electroplating is an art of protecting metal surface form corrosion and giving it pleasant appearance. 

Principle: Electrodeposition and redox reaction

Application:
  • Decorative purposes.
  • Industrial applications, e.t.c.
Reference
  • Kerri, Ken. 1986. Treatment of Wastewater from Electroplating, Metal Finishing and Printed Circuit Board Manufacturing. California: California State University.
  • Electroplating-Chemistry LibreTexts.html 
  • Electroplating-Wikipedia.htm
  • Electroplating-Definition, Process & Uses_Chemistry@TutorVista.com
  • Electroplating.html
  • Treating Plating Wastewater Products Finishing.html
*Sumber: Poppy
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