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New ship being prepared for launch, showing fresh anti-fouling paint Ship hull being cleaned of fouling in drydock. Anti-fouling paint is a specialized category of coatings applied as the outer (outboard) layer to the hull of a ship or boat, to slow the growth of and facilitate detachment of subaquatic organisms that attach to the hull and can affect a vessel's performance and durability.
The white patches visible on the ship's hull are zinc block sacrificial anodes. Cathodic protection on ships is often implemented by galvanic anodes attached to the hull and ICCP for larger vessels. Since ships are regularly removed from the water for inspections and maintenance, it is a simple task to replace the galvanic anodes.
In brief, corrosion is a chemical reaction occurring by an electrochemical mechanism (a redox reaction). [1] During corrosion of iron or steel there are two reactions, oxidation (equation 1), where electrons leave the metal (and the metal dissolves, i.e. actual loss of metal results) and reduction, where the electrons are used to convert oxygen and water to hydroxide ions (equation 2): [2]
In-water cleaning, also known as in-water surface cleaning, is a collection of methods for removing unwanted material in-situ from the underwater surface of a structure.. This often refers to removing marine fouling growth from ship hulls, but also has applications on civil engineering structures, pipeline intakes and similar components which are impossible or inconvenient to remove from the ...
Deoxidization is a method used in metallurgy to remove the rest of oxygen content from previously reduced iron ore during steel manufacturing. In contrast, antioxidants are used for stabilization, such as in the storage of food.
Similarly, sacrificial bars of a metal such as aluminium or aluminium alloys can be attached to an oil rig or to the hull of a ship to prevent it from rusting and breaking down. Magnesium may similarly be used on dry land for installations such as pipelines and oil refineries, where its high driving voltage is better for overcoming the ...
Pickling is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, and rust or scale from ferrous metals, copper, precious metals and aluminium alloys. [1] A solution called pickle liquor , which usually contains acid , is used to remove the surface impurities.
Iron and copper oxides can penetrate deep into the pores of ceramics and stones and create reddish-brown to black stains (iron oxide) and blue-green stains (copper oxides). The use of EDTA salt solution can be used to remove the oxides. A mild solution consists of 3% to 5% of EDTA; 15% to 20% solution in water on ceramics to remove the stains.