Rust Removal with Electrolysis - A Detailed Illustrated Tutorial, page 3
1. Introduction to Electrolysis Rust Removal:
What is Direct Current? What is Electrolyte? What is an Electrode?
3) What is Direct Current?
Electric current is a flow of electric charge carried by moving electrons in a conductor such as wire, or by ions in an electrolyte, or by both ions and electrons in a plasma. The SI (International System) unit for measuring the electric current is the Ampere, often shortened to amp, having a symbol "I". Electric current is measured by using an Ammeter.
There are two basic types of electric current: Direct Current (DC) and Alternating Current (AC). Direct current (DC) is the unidirectional flow of electric charge, i.e. the flow of electric charge is only in one direction. In Alternating Current (AC), the movement of electric charge periodically reverses direction and, therefore, cannot be suitable for the electrolysis cleaning. The electric power distribution and audio and radio signals carried on electrical wires are examples of alternating current.
Direct current is produced by such sources as batteries, battery chargers, thermocouples, solar cells, and is used to charge batteries, and in nearly all electronic systems, as the power supply. Most automotive applications use DC (although the alternator is an AC device). In electrolysis, an external direct current (DC) supply provides the energy necessary to create or discharge the ions in the electrolyte.
4) What is Electrolyte?
In simple words: Electrolyte is a solution that conducts electricity.
In electrochemical terms: Electrolyte is a substance containing free ions which are the carriers of electric current in the electrolyte. If the ions are not mobile, as in a solid substance, then electrolysis cannot happen.
The electrolyte is usually a solution of water or other solvents in which acids, bases, and salts are dissolved. You may have heard the term "electrolyte" associated with car batteries and capacitors.
When driven by an external voltage applied to the electrodes, the electrolyte provides ions (electrically charged atoms) that flow to and from the electrodes, where charge-transferring reactions can take place. Anion - a negatively charged ion that migrates to a positive electrode in electrolysis. Cation - a positively charged ion that moves toward the negative electrode in electrolysis. The decomposition of any inert chemical compound in the solution is possible only if a sufficient electric charge of the correct polarity is applied.
The electrolyte itself is not involved in any reactions other than to conduct electricity and to provide an ionic environment. Distilled and de-ionized water will not conduct electricity. Tap water is a poor conductor because it contains only a few ions (see details in the "How To Make An Electrolyte" section on page 15).
5) What is an Electrode?
Electrode is an electrical conductor which provides the physical interface between the external DC power supply providing the energy and the electrolyte.
Electrodes of metal and graphite are used in any electrolysis device. Electrodes that are placed farther apart in the solution will allow less current to flow. Electrolysis involves two types of electrodes: Anode and Cathode.
In the ELECTROLYTICAL DEVICE, the Anode is the POSITIVE (it has a deficit of electrons) terminal (color code - red), to which negatively charged ions (anions) travel when a direct current is passed through the electrolyte. Oxidation reactions (anions are oxidized by losing electrons) occur at the anode, and one of the products - oxygen, is evolved bubbling out. If the anode is accidentally immersed into an electrolyte, it will disintegrate as its metal will be turning into positive ions going into the electrolyte.
The Cathode is a NEGATIVE (it has a surplus of electrons) terminal (color code - black, gray or white) in the electrolytic setup, to which positively charged ions (cations) travel. At the cathode, reduction reactions (cations are reduced by gaining electrons) take place, and one of the products - hydrogen, is evolved bubbling out. If the cathode is immersed into an electrolyte, it will be plated with freshly-reduced ions that come out of the electrolyte (see details in the "Placing Electrodes into Electrolyte Properly" section on page 19). In the electrolysis derusting, all iron artifacts are attached to the CATHODE.
Some metals, such as platinum, and graphite do not usually participate in electrolysis reactions. This means that the anode will not be consumed over time, and, therefore, will last for years. Stainless steel (contains ≥10.5% chromium) will last less time than platinum or graphite, but much longer than any plain steel (contains ≤2.1% carbon; low alloy) (see details in the "Anodes - Sacrificial Electrodes" section on page 9).
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