1-	What is Corrosion ?
2-	What is Cathodic Protection ?
3-	What is Sacrificial Anode ?
4-	What are the types of Sacrificial Anodes ?
5-	How to make Galvanic Potential Series inside the sea water ?

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1- What is Corrosion ?
	Corrosion which is the metal's loss of metalic specialities, is a result of chemical and electrochemical reactions between the metal and the environment. Most of the metals are not enduring againist the effects of water and atmosphere and can easily be corroded under normal conditions. Except some of the inert metals all of the metals and their alloys corrode more or less. Corrosion can be seen in all parts of industry. Tanks that are in open air, depots, columns, parapets, vehicles, underground pipe lines, reinforced concrete irons, port legs, ships, chemical liquid pots in factories, pipes and many machine parts are faced with corrosion. All of these constructions become unserviceable because of corrosion and economical loss occurs.
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2- What is Cathodic Protection ?
	Cathodic Protection is making the metal construction which has to be protected, a catode of a electrochemical cell and stopping of anodical reactions which occur on the metal surface. Cathodic Protection 's purpose is the polarization of potential of the metal to be protected to the open circuit potential of the anode. To do this, an impressed current is applied to the metal in the catodical direction. There has been great development in Cathodic Protection which began to be applied in 1930s, and has been the most effective and economical way againist corrosion. The first application of Cathodic Protection was in oil pipe lines. Today a lot of metal constructions like port legs, ships, water and oil storage tanks, chemical material pots, heat changers, reinforced concrete irons, etc. are protected catodically. Especially in order to operate high pressured oil and natural gas pipe lines safely, Cathodic Protection is necessary. Cathodic Protection divides into two as impressed current sourced and sacrificial anoded. a- Impressed Current Sourced Cathodic Protection impressed curent sourced Catodic Protection is made as an outer direct current is applied to the metal. Direct current (-) end which is supplied from a transformator redressor system, is tied to the metal to be protected and the (+) end to a auxiliary anode. b- Sacrificial Anode Cathodic Protection In sacrificial anode cathodic protection systems the metal to be protected is tied with a metal (anode) which has less negative potential. So a galvanic cell is formed.by this way metal construction is made catode. By dissolving galvanic anodes produce current like a cell. The electrons which occur by the dissolvement of anode, supply the electrons which are necessary for catodical reaction by moving from outer connection to the catode (protected metal construction).
	Current capacities and efficiency of sacrificial anodes are definite. The surface of the metal construction to be protected can be kept as cathode by connecting adequate amount and number of galvanic anodes to the cathodic protection circuit. The usage field of Catodic Protection : Pipe Lines: Fresh water pipe lines, natural gas pipe lines, waste water pipes, undersea pipes, fire hidrant pipe lines, oil pipe lines. Inner sea constructions and vehicles: Ships, ferryboats, sea buses, submarine, yachts, harbour, port, platform, stake legs, float, etc.
	Tanks : Underground LPG and fuel tanks, ground fuel tanks, waste water tanks, fresh water storage tanks, etc.
	Water systems : Cooling and heating heat transfer systems, water heating systems,stream boilers, boiler tanks v.s.
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3 - What is Sacrificial Anode ?
	Sacrificial anode which is used to protect a construction as catodic is an current producer electrode by dissolving into positive ion. If you connect a more active metal like sacrificial anode to a metal ,which is exposed to corrosion, the electrons (which is need to catode reaction) obtains from sacrificial anode's metal automatical self oxidation reaction. So all of the anodic reactions on the surface of the protected metal lasts. Cathodic protection with sacrificial anode is based on this principle. To protect a steel pipe line catodically with sacrificial anodes, a more active metal like magnesium anode is connected to the pipe line. So in this galvanic cell, magnesium becomes anode, and the steel pipe cathode. In the anode by dissolving magnesium makes out electron. These electrons supply the electron necessity of catodic reaction. For the system to work automatically there has to be a potential difference that is enough to overcome the circuit resistency between the anode and cathode.
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4 - What are the types of Sacrificial Anodes ?
	Ther is three kind of anodes. Magnesium anode, zinc anode and aluminium anode .
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5 - How to make Galvanic Potential Series Inside The Sea Water ?
	Galvanic potential values are given below. If a pair of metals in the list is connected in sea water the metal above the table becomes anode and corrodes.
	Galvanic Potential Series Inside The Sea Water ( vs SCE )
	Magnesium -1.48 V Zinc -1.03 V Aluminium -0.79 V Wrought iron and carbon steel -0.61 V Cast iron -0.60 V Stainless steel type 430 AISI ( 17 % Cr ) -0.57 V Stainless steel type 304 AISI (18 % Cr,18 % Ni) -0.53 V Rolled brass -0.40 V Rolled brass (% 80 Copper) -0.38 V Copper -0.36 V Aluminium brass -0.32 V Nickel -0.20 V Titanium -0.15 V Monel -0.08 V
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