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A galvanic anode, or sacrificial anode, is the main component of a galvanic cathodic protection system used to protect buried or submerged metal structures from corrosion. They are made from a metal alloy with a more "active" voltage (more negative reduction potential / more positive oxidation potential ) than the metal of the structure.
Aluminum sacrificial anodes (light colored rectangular bars) mounted on a steel jacket structure. Zinc sacrificial anode (rounded object) screwed to the underside of the hull of a small boat. Cathodic protection (CP; / k æ ˈ θ ɒ d ɪ k / ⓘ) is a technique used to control the corrosion of a metal surface by making it the cathode of an ...
The capacity of a sacrificial metal may be calculated from first principle as follows: 1 kg Al = 1000/27 moles Al; 1 kg Al = 3 x 1000/27 moles of electrons; 1 kg Al = 3 x 1000/27 x 96494 coulombs of charge (by Faraday principles) = 10.72 x 10 6 Amp.seconds of charge per Kg Al (1 Coulomb = 1 Amp.Second) = 10.72 x 10 6 /3600 = 2978 Amp.Hours per Kg
The galvanic series (or electropotential series) determines the nobility of metals and semi-metals.When two metals are submerged in an electrolyte, while also electrically connected by some external conductor, the less noble (base) will experience galvanic corrosion.
A sacrificial part is a part of a machine or product that is intentionally engineered to fail under excess mechanical stress, electrical stress, or other unexpected and dangerous situations. The sacrificial part is engineered to fail first, thus breaking the serial connection and protecting other parts of the system downstream.
Anodic protection (AP) otherwise referred to as Anodic Control is a technique to control the corrosion of a metal surface by making it the anode of an electrochemical cell and controlling the electrode potential in a zone where the metal is passive.
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Zinc acts as a sacrificial anode for protecting the iron (steel). While steel is close to E SCE = -400 mV (the potential refers to the standard Saturated calomel electrode (SCE), depending on the alloy composition, electroplated zinc is much more anodic with E SCE = -980 mV.