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What are the factors that cause metal rust in the rust treatment

2016/06/21 09:57
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(1)atmosphericrelativehumidityAtthesametemperature,theatmosphericwatervaporcontentandthepercentageofwatervaporsaturatedcontent,calledrelativehumidity.Inarelativehumiditybelowthemetalcorrosionrateisverysmall,buthigherthanthatofrelativehumidity,thecorrosionspeedsuddenlyincreased.Thisrelativehumidityiscalledthecriticalhumidity.Thecriticalhumidityofmanymetalsisbetween80%and50%,andthesteelisabout75%.TheeffectofatmosphericrelativehumidityonCorrosionofmetalisthebiggest.Whentheairhumidityishigherthanthecriticalhumidity,themetalsurfacewillappearwaterfilmordropsofwater,iftheatmospherecontainingharmfulimpuritiesdissolvedinwater,theelectrolytemembranedrops,aggravatecorrosion. (2)airtemperatureandhumidityTherelationshipbetweenairtemperatureandhumidityaffectsthecorrosionofmetal.Herearesomeofthefollowing:first,theatmosphericwatervaporcontent,withtheincreaseintemperatureandincrease;second,thehightemperaturetopromotecorrosion,especiallyinthehumidenvironment,thehigherthetemperature,thefasterthecorrosionrate.Whentherelativehumidityislow,theeffectofthetemperatureonthecorrosionisnotobvious,butwhenthetemperatureishigherthanthecriticalhumidity,theamountofcorrosionincreasesrapidly.Inaddition,ifthereisadifferencebetweentheatmosphereandthemetal,thetemperatureislowinthemetalsurfaceoftheformationofcondensationwater,butalsoleadtorust. (3)corrosivegasesCorrosivegaspollutionintheair,withthegreatestimpactofsulfurdioxideonmetalcorrosion,especiallytheharmespeciallytosteel,copperanditsalloys.Sulfurdioxideintheatmosphereismainlyderivedfromthecombustionofcoal.Atthesametime,thecombustionproductsofcarbondioxidealsohasacorrosiveeffect.Corrosivegasesmixedintheatmospherearoundtheplant.Suchashydrogensulfide,ammonia,hydrochloricacidgasandsoonarethefactorstopromotethecorrosionofmetal.Ofcourse,theatmosphereofoxygeninthemetalcorrosionisthemostcommon,andatanytimeanywhere,itisself-evident. (4)otherfactorsTheatmospherecontainsalotofdust,suchassmoke,ash,chlorideandotheracid,alkaliandsaltparticles,someitselfiscorrosive,orwatercondensationnuclei,arealsofactorssuchascorrosion,corrosionofmetalchloridesareconsideredas"enemies".
(1) atmospheric relative humidity
At the same temperature, the atmospheric water vapor content and the percentage of water vapor saturated content, called relative humidity. In a relative humidity below the metal corrosion rate is very small, but higher than that of relative humidity, the corrosion speed suddenly increased. This relative humidity is called the critical humidity. The critical humidity of many metals is between 80% and 50%, and the steel is about 75%. The effect of atmospheric relative humidity on Corrosion of metal is the biggest. When the air humidity is higher than the critical humidity, the metal surface will appear water film or drops of water, if the atmosphere containing harmful impurities dissolved in water, the electrolyte membrane drops, aggravate corrosion.
(2) air temperature and humidity
The relationship between air temperature and humidity affects the corrosion of metal. Here are some of the following: first, the atmospheric water vapor content, with the increase in temperature and increase; second, the high temperature to promote corrosion, especially in the humid environment, the higher the temperature, the faster the corrosion rate. When the relative humidity is low, the effect of the temperature on the corrosion is not obvious, but when the temperature is higher than the critical humidity, the amount of corrosion increases rapidly. In addition, if there is a difference between the atmosphere and the metal, the temperature is low in the metal surface of the formation of condensation water, but also lead to rust.
(3) corrosive gases
Corrosive gas pollution in the air, with the greatest impact of sulfur dioxide on metal corrosion, especially the harm especially to steel, copper and its alloys. Sulfur dioxide in the atmosphere is mainly derived from the combustion of coal. At the same time, the combustion products of carbon dioxide also has a corrosive effect. Corrosive gases mixed in the atmosphere around the plant. Such as hydrogen sulfide, ammonia, hydrochloric acid gas and so on are the factors to promote the corrosion of metal. Of course, the atmosphere of oxygen in the metal corrosion is the most common, and at any time anywhere, it is self-evident.
(4) other factors
The atmosphere contains a lot of dust, such as smoke, ash, chloride and other acid, alkali and salt particles, some itself is corrosive, or water condensation nuclei, are also factors such as corrosion, corrosion of metal chlorides are considered as "enemies".