What makes rust?

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My understanding of rust is: oxidation on iron. Water or ache two oh comes in contact with iron, hydrogen is released into the atmosphere and the oxygen oxidizes the iron and makes rust. Does Anybody have anything add, correct, critique or anything?One more thing; I beleive red soil contains iron. It gets rained on and oxidizes.On a side note, hydrogen can be created using water and a Zinc catalyst.
Reply:Water contains dissolved oxygen separate from H*2O.  That is the entity causing the rust.  That is why boilers have a deaerator  ( http://en.wikipedia.org/wiki/Deaerator  ), pure water is relatively innocuous as as a corrosive agent.Red soil probably contains iron, not rust but various other hydrous iron oxides.  The iron is probably derived from the earlier weathering of minerals which contain iron such as pyroxene, amphibole, clay or mica.http://en.wikipedia.org/wiki/Red_bedsA oxygen-acetylene or oxygen-propane torch is also causing the a rust in its simplest form and reaction  Fe+O*2  -->  Fe*2 0*3  + heat
Reply:From How Stuff Works:For iron to become iron oxide, three things are required: iron, water and oxygen. Here's what happens when the three get together:When a drop of water hits an iron object, two things begin to happen almost immediately. First, the water, a good electrolyte, combines with carbon dioxide in the air to form a weak carbonic acid, an even better electrolyte. As the acid is formed and the iron dissolved, some of the water will begin to break down into its component pieces -- hydrogen and oxygen. The free oxygen and dissolved iron bond into iron oxide, in the process freeing electrons. The electrons liberated from the anode portion of the iron flow to the cathode, which may be a piece of a metal less electrically reactive than iron, or another point on the piece of iron itself.The chemical compounds found in liquids like acid rain, seawater and the salt-loaded spray from snow-belt roads make them better electrolytes than pure water, allowing their presence to speed the process of rusting on iron and other forms of corrosion on other metals."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:That was interesting Rock Knocker and the part about the OA causing rust brings me to another question and subject that was brought up here before. One of Old Timers claimed that there is water in Iron. He claimed that heating with an OA torche caused water to come out. Others claimed it was condensation from the heat. My thoughts were and Ive never said this before and its just a theory but; if there is any hydrogen trapped in the iron(hydrogen imbritlment) then the heat (heat of formation) and the oxygen in the air or from the torch created the water. In other words, the Old Timer was half rite.  What are your thoughts and do you remember what old timer it was?Good xplanation Oldendum and what do you think about water trapped in iron?Last edited by Insaneride; 02-13-2014 at 10:29 AM.
Reply:No basis for any of the above, there is no water and very little hydrogen trapped in iron (steel) even in the most egregious cases of hydrogen embrittlement.Rust can occur without water.  Go look inside a boiler, there can be massive corrosion on steel, on the firebox side, far way from any contact with water.  There is free oxygen in the flue gas, and it has increased chemical reactivity because it is hot.  The result is rust in the absence of water.
Reply:There's no water trapped in iron, not in the sense I think you mean.  The water you see on the surface of a plate, when heating it with a cutting torch or rose bud, is water produced as a by-product of combustion.  Burning a fuel gas makes water and that water condenses on the plate from the hot gases produced by the combustion process.  It's the same phenomenon as water condensing from the air on a cold glass of beer or soda.    The water disappears as the steel heats up because the plate grows hot enough that water will no longer condense on the surface.  This is also why water drips from the exhaust system of your car when you first start it up. Once the whole exhaust system is hot, the water stays in the exhaust gases and doesn't condense in the cats, muffler, and exhaust tubing.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Water trapped in iron.  No.  Referring to the phenomenon of heating a piece of iron with a torch that uses fuel and oxygen combustion causing water to appear on the surface when the flame is first applied to the iron:  The momentary presence of water on the surface of the iron is simply water vapor byproduct of combustion from the flame condensing on the cool surface of the object.  The exact same process is what causes water to blow from the exhaust tail pipe of an automobile after a cold start in chilly temperatures.  The water vapor is a by product of combustion and when the gases in the exhaust stream are ejected into the cold exhaust system surfaces, the water vapor condenses on those surfaces.  The exhaust "wind" naturally carries the condensed liquid water along the length of pipes until it emerges and drips out the tail pipe.  As the pipes heat up, the condensing region in the exhaust system moves further and further away from the engine and closer to the tail pipe.  After the entire length of the exhaust system has been heated to a higher temp than can support condensation, the water vapor in the exhaust stream is carried completely through without condensing any liquid water, but you can see the cloud of "steam" in the frosty air behind the tail pipe.Same process you see with a torch on cold metal.  The water you see is from the combustion process.By the same token of facts, if you direct a flame from an oxy/fuel torch onto a piece of aluminum, or brass, or lead, or other metal........you will also see the brief presence of water as it condenses on the cool surface of the object.I don't know who the Old Timer was that remarked about water in iron coming out due to heating.  Would that old timer also say that windows fog up when you exhale on them because the glass had water in it that came out because you blew your hot breath on the glass?A dab will do nailed it before I got my post up, I have had to explain the phenomenon of combustion water many times down through my many years.Last edited by walkerweld; 02-13-2014 at 11:05 AM.
Reply:@ Insaneride - H, O, and time from the Earth interacting with Fe-C material.  Redux.  Same reason an apple, when bitten, begins to "oxidize."  Enzymic reaction."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:All good xplanations and there is no water in steel got it. Water is formed thru combustion and condensate.I do understand that rust forms without water but; when water is used, does the hydrogen go into the atmosphere, the iron or entropy?
Reply:When water is involved as a catalyst to rust, neither the hydrogen or the oxygen of the water molecule is used, and the water molecule stays intact.  The oxygen is derived from atmospheric or dissolved oxygen in solution.There are geochemical weathering reactions that do result in the water molecule breaking up, but not in the simplest formation of rust from steel.
Reply:Don't forget that existing rust leads to more rust! At least, that's if I remember correctly. I'm pretty sure that if you paint over rusted iron/steel, the iron/steel will still continue to rust beneath the paint. I don't have much experience with stuff like that though, so I may be wrong.Different alloys also have different amounts of resistance to rusting. From what I've read, alloys such as tool steel tend to be EXTREMELY susceptible to rust, while other alloys can handle a fair amount of sitting in water before rusting. In addition, stainless steel alloys aren't quite 'stainless' so much as 'stains less' (to paraphrase something I read somewhere online). Stainless steel WILL eventually rust or otherwise corrode, but not nearly as fast as other alloys. If I remember correctly, the rust resistance comes from the chromium in the alloy oxidizing and forming a protective layer that conveniently happens to block oxygen from getting through and causing rust. If the underlying metal is somehow exposed (such as by cutting a block of stainless steel in 2 pieces), the chromium in the alloy will form another protective layer.Oh, and iron/steel rusting is an exothermic reaction. Theoretically, if you can get the iron/steel into a dust form, have sufficient oxygen (water vapor might be neccessary as well, I'm not sure), and a source of ignition, you should be able to get the iron/steel dust to explode. This is a result of the iron/steel dust having a massively higher surface area compared to blocks of iron/steel, thus allowing a much faster rate of rusting. It works for other metals as well. A safer example would be to light some steel wool on fire. There isn't much of a flame, but it'll burn. It's similar to dissolving powdered Nesquik in milk. The nice powder dissolves pretty quickly, but the chunks take a while to dissolve because the outer layer has to dissolve before the inner powder can dissolve.
Reply:It's not theory, it's fact.  Metal powders WILL EXPLODE.http://www.metal-powder.net/view/188...atin-facility/Speculation that it was due to a gas leak was found not to be the cause.  It was due to unacceptably high concentrations of airborne powdered metal.Last edited by walkerweld; 02-13-2014 at 12:58 PM.
Reply:how much airborne powdered metal has to be present to explode? I do a lot of cutting with abrasive wheels and have dust settling on everything in my shop at a good rate.Lincoln 225 ac (my first machine)farmhand 115vac 70amp mig/fc toymiller aead 200le (my main machine)
Reply:Originally Posted by InsanerideThat was interesting Rock Knocker and the part about the OA causing rust brings me to another question and subject that was brought up here before. One of Old Timers claimed that there is water in Iron. He claimed that heating with an OA torche caused water to come out. Others claimed it was condensation from the heat. My thoughts were and Ive never said this before and its just a theory but; if there is any hydrogen trapped in the iron(hydrogen imbritlment) then the heat (heat of formation) and the oxygen in the air or from the torch created the water. In other words, the Old Timer was half rite.  What are your thoughts and do you remember what old timer it was?Good xplanation Oldendum and what do you think about water trapped in iron?
Reply:Originally Posted by InsanerideAll good xplanations and there is no water in steel got it. Water is formed thru combustion and condensate.I do understand that rust forms without water but; when water is used, does the hydrogen go into the atmosphere, the iron or entropy?
Reply:All you need to form rust is any truck I own Either that or it's my yard - pretty sure I can watch them rust just sitting there Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Automakers didn't invent rust, but quickly saw the value of it."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Originally Posted by OldendumThe chemical compounds found in liquids like acid rain, seawater and the salt-loaded spray from snow-belt roads make them better electrolytes than pure water, allowing their presence to speed the process of rusting on iron and other forms of corrosion on other metals.[/I]
Reply:Originally Posted by OldendumAutomakers didn't invent rust, but quickly saw the value of it.
Reply:Originally Posted by MinnesotaDaveAll you need to form rust is any truck I own Either that or it's my yard - pretty sure I can watch them rust just sitting there
Reply:Originally Posted by MinnesotaDaveWish someone would bring me something rusted and broken - getting bored lately  ...
Reply:while we're exploring the old wive's (wife's?) tales of welding and not to hijack this thread BUT i remember hearing that cutting with oxy/acet is just a controlled or faster form of rusting? any of the maven's of metal here ever heard of that?i.u.o.e. # 15queens, ny and sunny fla
Reply:Originally Posted by docwelderwhile we're exploring the old wive's (wife's?) tales of welding and not to hijack this thread BUT i remember hearing that cutting with oxy/acet is just a controlled or faster form of rusting? any of the maven's of metal here ever heard of that?
Reply:Originally Posted by OldendumMy son has an old Toyota truck that originated in NJ.  Has one hole in the frame under the cab that you could stick a large orange into.  Maybe you could cut a hole where the frame rail curves up and shove a few pieces of bed frame angle in there and weld it up.  Or maybe we should get a really long leaf spring and connect it to the front and rear suspension and just put in a few bolts here and there along the bottom of the frame.
Reply:leaf spring might be hard to drill through also i'm not sure welding to it would work either. bed frame angle is always an option though. doesn't every welder have a few frames stashed away for a rainy day repair?i.u.o.e. # 15queens, ny and sunny flaOriginally Posted by docwelderwhile we're exploring the old wive's (wife's?) tales of welding and not to hijack this thread BUT i remember hearing that cutting with oxy/acet is just a controlled or faster form of rusting? any of the maven's of metal here ever heard of that?
Reply:.... rust never sleeps ....
Reply:Originally Posted by MinnesotaDaveThat's easy stuff - I keep that size bed frame in stock leaning against the shop wall...it has a nice rust color patina and takes a weld perfectly with minimal prep...if it's too thin I hammer the angle flat first.I don't fix frames using leaf spring iron though, my second choice is squared off oak logs wrapped with log chain and an approved binder.
Reply:Originally Posted by MinnesotaDaveThat's easy stuff - I keep that size bed frame in stock leaning against the shop wall...it has a nice rust color patina and takes a weld perfectly with minimal prep...if it's too thin I hammer the angle flat first.I don't fix frames using leaf spring iron though, my second choice is squared off oak logs wrapped with log chain and an approved binder.
Reply:Originally Posted by Willie BRail road ties last longer there's a world of uses for rails, and spikes. Best to not use the ones in use.
Reply:Originally Posted by docwelderi do believe you need water to form rust.
Reply:Iron and oxygen are the involved chemicals, water is a catalyst for rust because a catalyst only speeds up a reaction.  Iron (steel) is stable in the presence of oxygen, it needs a "catalyst" ( not the correct term in this usage, but close enough ) for iron to oxidize.  Aqueous water, saline solutions, humidity, very high partial pressures of oxygen, high oxygen atmospheric  percentage or heat on the order of several hundred degrees.
Reply:My high school chemistry teacher said burning steel accelerates the process, but is much the same as rust. This of course is the same teacher I asked why water speeds rust, his response; "I don't know". I think he was an idiot A young man in Vermont wants to know about rust, if a teacher wants to sieze the interest of a student, address subject matter he cares about. Were I in his position, I'd damned well find out!
Reply:There are several versions of iron oxide Fe2O3. Is only one.  An interesting one to see water soaked sheets stacked together.  The iron oxide is black in colour.  One thing that amazed me was that below 40 deg F. The rate of oxidation falls off rapidlyAlso corrosion and rust is helped by moisture(electrolyte) and dissimilar metal forming a crude battery.Even a weld bead is different enough to cause corrosion between the weld and parent metal.Also food for thought.  A barge or tank that has bee closed up for years will have no oxygen inside.  The rusting steel consumes itLast edited by lotechman; 02-14-2014 at 10:24 PM.
Reply:Originally Posted by Willie BMy high school chemistry teacher said burning steel accelerates the process, but is much the same as rust. This of course is the same teacher I asked why water speeds rust, his response; "I don't know". I think he was an idiot A young man in Vermont wants to know about rust, if a teacher wants to sieze the interest of a student, address subject matter he cares about. Were I in his position, I'd damned well find out!
Reply:A physics prof told the class that:  the reason ice floats is God didnt want the fish to die. All life depends on the xpansion of water whenever it freezes. otherwise we would all die. Everything else shrinks in the cold.  No pun haha.I believe water xpands because in Gods version and isometric 3D Lewis structures God made water xpand
Reply:A physics prof told the class that:  the reason ice floats is God didnt want the fish to die. All life depends on the xpansion of water whenever it freezes. otherwise we would all die. Everything else shrinks in the cold.  No pun haha.I believe water xpands because in Gods version and isometric 3D Lewis structures God made water xpandI asked Jievws why water floats and xpands when frozen and , he said, " good wuestion". Is this debatable?
Reply:Originally Posted by lotechmanThis is someone you can learn from.  He is not afraid to admit he does not know everything.
Reply:Originally Posted by InsanerideA physics prof told the class that:  the reason ice floats is God didnt want the fish to die. All life depends on the xpansion of water whenever it freezes. otherwise we would all die. Everything else shrinks in the cold.  No pun haha.I believe water xpands because in Gods version and isometric 3D Lewis structures God made water xpand
Reply:Originally Posted by InsanerideA physics prof told the class that:  the reason ice floats is God didnt want the fish to die. All life depends on the xpansion of water whenever it freezes. otherwise we would all die. Everything else shrinks in the cold.  No pun haha.I believe water xpands because in Gods version and isometric 3D Lewis structures God made water xpandI asked Jievws why water floats and xpands when frozen and , he said, " good wuestion". Is this debatable?