Corrosion Definition and 100 Threads

Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, carbonate or sulfide. It is the gradual destruction of materials (usually a metal) by chemical and/or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion.
In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfates. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the original metal and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases.
Many structural alloys corrode merely from exposure to moisture in air, but the process can be strongly affected by exposure to certain substances. Corrosion can be concentrated locally to form a pit or crack, or it can extend across a wide area more or less uniformly corroding the surface. Because corrosion is a diffusion-controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the exposed surface, such as passivation and chromate conversion, can increase a material's corrosion resistance. However, some corrosion mechanisms are less visible and less predictable.
The chemistry of corrosion is complex; it can be considered an electrochemical phenomenon. During corrosion at a particular spot on the surface of an object made of iron, oxidation takes place and that spot behaves as an anode. The electrons released at this anodic spot move through the metal and go to another spot on the metal and reduce oxygen at that spot in presence of H+ (which is believed to be available from H2CO3 formed due to dissolution of carbon dioxide from air into water in moist air condition of atmosphere. Hydrogen ion in water may also be available due to dissolution of other acidic oxides from the atmosphere). This spot behaves as a cathode.

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  1. J

    Understanding the Role of Ions in Corrosion of Metals in Aqueous Environments

    I have some questions concerning the tendency of a system containing two different metals and water to corrode. This is coming from several similar discussions on another forum, concerning water cooling of computer components. There seems to be a lot of repeated dogma, which may include...
  2. F

    How to calculate corrosion rate?

    1. Homework Statement Iron sample with dimensions 10mm x 20mm x 2mm is exposed to a corrosive environment (neglect thickness for surface area). Both sides of the sample are exposed to corrosive environment. Given http://i.imgur.com/tGRw4.jpg" (a) Calculate corrosion rate mm/y (b)...
  3. F

    How Do You Calculate the Corrosion Rate of an Iron Sample?

    Homework Statement Iron sample with dimensions 10mm x 20mm x 2mm is exposed to a corrosive environment (neglect thickness for surface area). Both sides of the sample are exposed to corrosive environment. Given http://i.imgur.com/tGRw4.jpg" (a) Calculate corrosion rate mm/y (b) Calculate...
  4. B

    Exploring the Best Brass for Corrosion: Types, Properties, and Experiment Design

    Homework Statement I have been given the task to corrode brass with common base, acid and salt. I understand that it is an alloy of copper and zinc and is actually designed not to rust. Before I begin the experiment, I am looking for the best TYPE of brass to use in this experiment. Given...
  5. S

    Aluminum Corrosion: How Long Will It Last?

    I've seen various documentaries where WWII-era aircraft wreckage has been sitting out in the jungles on Pacific islands for over sixty years and everything that is aluminum is in really good shape. Little bit of scrubbing the algae, mildew, and moss off of it, and it would look like new. I...
  6. B

    Fretting Corrosion: Resistance of Materials & Accelerated Life Test

    Fretting Corrosion I am researching a fretting corrosion problem and I am looking for resources on the relative resistance of materials to this phenomenon as the material on this subject seems very limited. The application is a rolling ball switch, which impacts the tube sidewall due to...
  7. D

    How important is maintaining mechanical tolerances for mil spec connectors?

    Aside from replacing a lightly corroded mil spec connector, does anyone have any experience in a process for cleaning them up? Myriadic or hydrochloric acid have been recommended, but my thoughts are that they will eat away at the plating... The connectors are either Aluminum Cad Plated...
  8. J

    UA Offers the First Corrosion Engineering Program

    The University of Akron's proposed new http://bit.ly/aujkcF" — the first bachelor's degree program of its kind in the United States — is moving closer to development due to $500,000 in funding from the U.S. Department of Defense (DoD)... Hi! I am an engineering student and I came across...
  9. A

    What Role Does Seawater and HCl Play in Electrochemical Corrosion?

    Hi there, So this isn't actually my homework, I've been assigned to TA an electrochemistry lab. Problem is, I know almost nothing about electrochemistry and although I've tried to learn I'm still a bit rusty (har har!). The lab involves immersing different electrodes in seawater in a single...
  10. Y

    What is a good reasearch topic to work on in the case of Corrosion?

    What is a good reasearch topic to work on in the case of Corrosion?? What is a good reasearch topic to work on in the case of Corrosion?? :rolleyes:
  11. A

    Electrical Wiring - corrosion, cracking and resistance.

    Homework Statement Been racking my brains over this one and I'm stuck maybe someone here can help me. I'm doing physics through distance education at high school and its very difficult. "In house fires the wiring is often cited as the cause of the fire. Often this wiring is partially...
  12. K

    Plant aging Steam Generator Corrosion

    Hi I am told that steam generator is an area that is suseptible to aging effects and corrosion. I was wondering if anyone can elaborate on this a bit. Is it just due to the heat and humididty? I am studying BWRs and safety and maintanced aspects and I was thinking of focusing on this area...
  13. V

    Does Calcium Build Up on Metal Enhance Corrosion?

    Hey Guys, Just curiosity, but if a metal surface has a build up of calcium does this mean there is a higher chance of corrosion occurring? Or can it accelerate corrosion? Or is the build up on the surface of metal generally harmless?
  14. 7

    Aluminum anodizing/coating, strength and corrosion resistance

    It's been awhile since I've been on, but I'm still working on my brake system for my track car - https://www.physicsforums.com/showthread.php?t=304215. I now have the hats and brackets machined, and I'm trying to decide what to do for the finish. At first I was set on anodizing as it'll...
  15. S

    What causes the increased corrosion rate in high temperature environments?

    What is the chemistry behind high temperature corrosion , and why is the corrosion rate higher .
  16. A

    Corrosion in Carbon Steel Pipes Due to Air Pressure

    Hi all, just a quick question, I saw some of the carbon steel pipes which are used to tranpsort compressed air are corroded, when i ask, people told me that the corrosion was caused by the air. Is it the moisture in the air which causes the corrosion, or can the air pressure (sorry, can't...
  17. M

    Help to visually identify a corrosion type

    Hi all, I work in the "product assurance" department for an automotive company, and we have encountered what looks to be a corrosion effect during a controlled test (85 degrees C and 85% relative humidity) on one of our components. I feel that my limited knowledge of chemistry is really...
  18. S

    Casual factors of corrosion failure?

    What are the casual factors of corrosion failure?
  19. G

    Anyone know of an internal liner material to protect against internal corrosion

    Does anyone have any experience with liner material for application on pipework with internal corrosion/erosion? Pipes are designed to hold water/methanol vapour Normal operating conditions for the pipes: Temperature • Average temp - 172F • Max temp - 267.1F Pressure • Average...
  20. U

    Corrosion Engineering Degree: Worth It?

    My school is offering the United State's first corrosion engineering degree, and I was curious if anyone knew just how useful that degree might be. The university makes it sound rather in demand, but I'd like to get an unbiased opinion. I've already finished my first year in Chemical...
  21. R

    Corrosion of Steel Pipe: Salt Water, Sand & Flow Rates

    What equations would show the process of corrosion of a steel pipe that is carrying salt water and sand and also would the corrosion rate be different if at different rates of flow?
  22. P

    Carbon content in steel and corrosion

    I have two questions about carbon steel. How does the carbon content of steel effect the rate of corrosion? Apart from providing strength to the steel, how does carbon effect the properties of steel?
  23. P

    Designing Corrosion Experiment for Steel, Aluminum & Iron

    I need to design an experiment which investigates the effect of corrosion on different materials used in marine vessels. I am testing three metals: Steel, Aluminum and Iron in 4 conditions: acidic solution + less acidic solution basic solution + less basic solution salt water +...
  24. P

    Corrosion Experiment Design: Alloys, Prevention & Marine Vessels

    Hello. I need to design an experiment(s) which investigates the factors which effect corrosion, the properties of different alloys used in past and modern industry and the ways in which corrosion may be prevented. This will then be used to make judgments regarding the most effective and...
  25. B

    Erosion Corrosion of Titanium Specimen

    Homework Statement Seawater at 13m/s containing 1750mg/L sand impinges on a 8cm^{}2 titanium specimen. I'm given a polarisation curve (which I'm unable to reproduce here for the moment) and the data that without cathodic protection a weight loss of 4.0mg is measured in 16 hours and with CP...
  26. D

    Pitting corrosion in spur gears

    Greetings, I decided to use a professional calculation package for machine design procedures in order to speed up the design process. This package somehow calculates a safety factor for pitting corrosion for spur gears. However I haven't been able to figure out how this is calculated. So far...
  27. G

    Very latest technique for corrosion control

    hiiiiii i want to know the very latest technique for corrosion control
  28. M

    Can sulphuric acid corrode steel and granite?

    HI, if I put some sulphuric acid on a 1.5" sheet of reinforced steel how long would it take until I could just poke the corroded area and it would go through? Also if I had a 4" sheet of granit and poured it on that would it corrode? And how long would it take? Pretty random question I know...
  29. A

    Why Do I Feel Rusty with Corrosion Knowledge?

    hi everyone... I want the experience of almost 14, if you could help to develop a website or memoirs of your College, I'll thank you
  30. S

    Caustic(Sodium Hydroxide) corrosion problem

    I am using castic as heating / Cooling media for the reactors in my lab. MOC of my reactor and pipeline is CS. Can anyone tell how to prevent / minimise this?
  31. J

    What Causes Corrosion on Car Battery Terminals?

    I know only a little about chemistry, but am curious as to what makes up the white/blue crystalized corrosion that sometimes gets into the terminals on car batteries? What reaction is happening, etc. Also, does the polarity of the terminal favor the reaction, one any more than the other + vs -...
  32. M

    How Do Power Lines Influence Underground Metal Corrosion?

    According to some technical recommendation, we must be concerned about metal under ground structures (e.g. pipe lines) corrosion in neighbor of power transmission lines. Sinusoidal high current elements can produce eddy induced currents in their surroundings .The eddy currents in electrical...
  33. A

    Corrosion of aluminum alloy 319.0 help

    Recently, we purchased a relatively brand new high performance car engine to swap with our regular car engine for the purpose of gaining more horsepower. I need to find out the probability of corrosion of an aluminum alloy (possibly 319.0) part of a complete engine block brought to the shop...
  34. C

    Corrosion - Passive films on 304/316L s/s?

    Hi All, In acidic conditions (pH not known, but do know there is presence of formic & sulphuric acid, chlorides + free water), is is possible for NiO to form in preference to CrO on Austenitic stainless steel - grade 304 or 316L? I have a sample analysis from within 304/316L stainless...
  35. D

    Corrosion Of Iron - Differential Aeration Principle

    Hi. In chemistry, we are currently studying electrochemical cells. We are doing corrosion at the moment. Corrosion of iron, to be specific. If i have a piece of iron exposed to the air, it will form a thin layer of iron oxide, right? However, this oxide will have fine cracks and be quite...
  36. F

    Definition & Source of Primary & Secondary Corrosion Inhibitors

    I'm looking for the definition of "Primary Corrosion inhibitor" and the source. Common sense tells me that primary corrosion inhibitor is the product you use to treat your primary corrosion problem. Secondary corrosion inhibitor, as the word say, is the product used as “safety” to prevent other...
  37. S

    Classification of corrosion, (Aviation Industry)

    Anyone know the detail about it? how we define the class of corrosion?
  38. J

    Copper Corrosion: Investigating Tourquise-Green Substance

    I put a copper pipe in a tank of water with dissolved iron in it and applied an electric current somthing like 6 volts at 1.5 amp and the pipe was hooked up to the positive terminal. After a couple of days some tourquise or pale green substance formed, i scraped this off and there was a copper...
  39. Astronuc

    High Strength Steel with Corrosion Resistance and High Toughness

    I periodically browse the literature for new products. In the August 2006 issue of Advanced Materials & Process (from ASM International), I found an article on a new high strength steel from Carpenter Technology Corp. (Cartech) Cartech Custom 465 (find it at www.cartech.com) Custom 465...
  40. S

    Does Electrochemical Potential Affect Corrosion Rates in Metals?

    I am pondering over how the rate of corrosion in metals are effected. Does E(V) of the reactions play an important part in this?
  41. S

    Corrosion of Steel: Equilibrium & Rate Drop

    Say is a piece of steel is placed in still water and is corroding. Why will the corrosion rate drop away after time?? Is it because the system reaches some sort of equlibrium??
  42. R

    What Should Be the Control in a Corrosion Experiment?

    Hi everyone, I need to do an experiment at home that tests different environmetnal conditions that facilitate corrosion of stainless steel and mild steel screws. I have 20 screws (10 stainless and 10 mild steel screws). Each screw will be in a separate container. One pair of srews will have...
  43. D

    Cars & Corrosion: 6 Testing Methods & Protection

    Here's some questions I need help with... Its about Cars & Corrosion 1. Name six ways that corrosion was tested on cars. 2. State two reasons that corrosion is not benificial. 3. How does ventilation stop corrosion? 4. In what way does mud contribute to corrosion? 5. What are the two...
  44. F

    Redox Corrosion: Explaining HMS Alarm's Surprising Results

    Anyways, can anyone help me with this question.. In 1763, the British Admirality covered wooden ship HMS Alarm with copper sheeting to protect it from marine worms. This was sucessful but, they reported: '... we were surprised to perceive the effect of the copper had upon iron where the two...
  45. S

    How to Prepare Notes on Corrosion, EMF Series, and Fossil Fuels?

    Hi Guys! im a student of electronics engineering (1st year). I have to prepare notes for my exams about the following topics. Please recommend me some websites from where i can prepare these notes. 1) Corrosion (Theories, Inhibition and Prevention) 2) EMF Series 3) Types of Fuels...
  46. S

    Dissolution of corrosion product over inconel 600 and SS304

    I would like to know why alkaline permanganate (potassium permanganate in sodium or potassium hydroxide) is used for dissolving corrosion products formed over nickel alloys such as inconel 600 (composition of alloy is 72% Ni, 16% Cr, 8% Fe) while acidic permanganate (potassium permanganate in...
  47. J

    How Can We Prevent Sand-Induced Corrosion in Tank Turbines?

    Hello. I'm a HS junior at a research summer program and am researching Jet Engines. Apparently, when Jet Engines are used in tanks which move in deserts , the sand enters the turbines and corrodes them. In order to prevent that, would the solution be to implement a closed system so there is no...
  48. wolram

    Corrosion on the cable fooled my test meter

    Yes i had two today, one was because corrosion on the cable fooled my test meter, the other was because a door swich knob was not in mechanical contact with the switch, two in one day is just not fair, i must be getting sloppy, as i have only had two others in my life ,but then i must...
  49. O

    Solving Corrosion & Heat Transfer Problems on Steel Vat Plated with Zinc

    I have a problem that I need to solve that is quite extensive it boils down to this. I have a steel vat that's been plated with zinc and its being used to store sulfuric acid. I have to find corrosion rates, heat transfer and thermal stresses, elastic and plastic deformation problems, hydrogen...
  50. K

    Corrosion Resources: Socioeconomic Implications & Prevention

    Hi all, I'm doing a project on socioeconomic implications of corrosion and prevention. Do you have any good websites where I can get information of this topic? It seems to me that it's kinda difficult to find relavent information from the internet. Any help would be appreciated. Thanks in...
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