why does painting of metal surface prevent corrosion?
139943
corrosion is normally the oxidation of the metal, painting it stops the air getting to the metal and therefore stops the oxidation.
379742
Galvanising iron is nothing but a process of coating iron with a thin layer of zinc by electroplating. The main idea behind this is that zinc is a 'sacrficial metal' as it is highly electropositive.\n\nWhat actually happens when you expose normal 'ungalvanized' iron to the atmosphere is that it reacts with oxygen and moisture to form a mixture of iron oxides(rust).\n\nOn the other hand, when galvanized iron is exposed to the atmosphere, it is in fact not the iron, but the ZINC which is exposed to the atmosphere. Now it is ZINC, which undergoes oxidation(not iron as in the case above). This leads to the formation of  a thin film of zinc oxide over the actual zinc(which was coated over iron). Zinc oxide acts as a protective layer and prevents further amount of zinc(or iron) from being exposed to the atmosphere.\n\nSo that's the whole story behind 'Why galvanized iron lasts longer than ordinary iron'. \n\nAnd 'IBL' or whoever you are, please do not copy essays from encyclopedias. Even if you do, have at least the minimum decency and courtesy to copy 'relevant' information.\n\nIt's an insult to ppl who really know chemistry out here.
789930
The process of galvanizing consists of coating metals, such as iron and steel, with a thin protective layer of zinc.  The layer of zinc provides protection to the metal from corrosion.  The result of galvanizing is a corrosion resistant product to be used for  many outdoor applications, where the weather is a factor in the life expectancy of the material.  The protective layer of zinc prevents the ferrous material from coming in contact with the oxygen causing oxidation.  Oxidation is the combination of a substance with oxygen, in iron and steel the main combination result is rust. Without this contact the ferrous material does not corrode.  An example of how this works is when iron reacts with oxygen it forms iron oxide (the main component in corrosion), however if the iron is galvanized the zinc reacts with oxygen causing zinc oxide prior to reaching the iron.  There are two types of oxide caused by iron, ferric oxide and ferrous oxide.\n\nThere are several ways to galvanize steel products, such as hot dip galvanize, electroplating galvanize, mechanical coating, zinc spraying, and zinc dust painting. In hot dip galvanize there are two different processes that are used.  One is the process of continuos hot dip galvanizing which consists of a start point and a finish point.  In between these two points the material never stops going from a raw material (iron/steel) to a finished good ready to be shipped. The other is stationary hot dip galvanizing in which an individual item is dipped into a pot of molten metal and removed. \n\n\n    The following steps are taken in hot dip galvanizing in both hot dip and continuous operations; cleaning, pickling, pre fluxing, galvanizing, cooling, finishing, inspected, and throughout the process the product is rinsed and air blown.  The main difference between the two (continuos hot dip and stationary) is that the material on a continuos operation is finished when the cycle is complete versus just dipping the material in most cases is hand finished to remove excess burs, runs, and bumps that are result of no external wipe (air knife, coal, etc.).\n\n\n=)
1131804
You have the potential for galvanic corrosion.  Essentially, two metals at different potentials share electrons and one metal (the one with the higher potential) will start to erode and "plate" the other metal.\n\nTypically, using some sort of material that is a non-conductor (ceramics, rubber, etc) between the two or passivating the metal surfaces or coating the metal surfaces (prime and paint per ANSI standards) are your best options to prevent this.
535149
Actually the copper doesn't come directly from the solution...\n\nNot sure how much detail you want, but it does use electroplating.  This means that it uses electricity to plate metal on an object.  The stainless steel object is put on the "positive end" and a lump of pure copper is placed on the "negative end."  A low voltage is used because a high voltage plates too fast, and the layer will peel off quickly.  If copper is the plating, then the solution must be a fairly low-concentration copper sulfate (CuSO4) solution, meaning that copper is the only metal present in the electrochemical cell.  The negative end is called the anode, and this decreases in mass as its copper ions are taken to the positive end -- the cathode.  \n\nThis method of plating multiple metals is actually fairly common, because the properties of each one can be combined.  Nickel can be used for farm equipment and engines because it can withstand a lot of force, silver is used for decoration, chromium is used to withstand a lot of use (like a spoon).  Copper is able to conduct heat and helps food cook evenly.
909393
B.\n\nthe process is called passivation. and may be increased to a greater extent on purpose by electrolysing aluminum in acid to increase the oxide layer. this is called anodizing.
1165664
As  far as I know, galvanizing involves coating metals like iron with zinc. If you understand redox, then zinc is a stronger oxidizing agent than iron i.e. it will react before iron gets a chance to become rust. When zinc reacts with water, it makes zinc hydroxide which coats the outer layer of the galvanized metal. Zinc hydroxide, unlike rust, doesn't look too bad and prevents any further reaction from occuring.
410825
Others have had similar problems and solved them.  See the link.  In general, metals (especially iron and its alloys) rust when exposed to moisture in the presence of oxygen.  The rust is a loose collection of molecules that allow more moisture and oxygen to reach the base metal.  For example, you can shine aluminum but it will quickly dull with oxidation.  The aluminum corrosion however forms a tenacious film that protect the metal from additional corrosion.  I heard that copper (flashing?) on a rooftop can cause aluminum gutters to corode.  Various alloys of iron (steel) including heat treatments may impart various corrosion properties, however, chrome is usually added to form stainless steels that best resists rusting.  Silicon steel may have to be protected.  Good luck.
1125460
You should consider/investigate electroless plating processes. \n\nHi-Phosphorous Electroless nickel is a continuous coating easily applied inside container/cavities like your teapot, and is reasonably affordable.  Contains mostly nickel with a minor amount of phosphorous - the high phosphorous version is quite corrosion resistant to many acids except sulphuric.  Low-phos and standard electroless are cheaper, but with lower corrosion resistance - these might work for you too - a little experimentation is worth doing.  Check around for prices at the plating shop - coating quality varies a lot.\n\nThere is an electroless gold plating process too (of high purity), but you can imagine it is more expensive and is porous at the microscopic level, so doesn't give you the corrosion resistance you might otherwise expect.  It is very possible to combine the two: modestly thin gold (10-30um) on top of nickel, and then you'd have a pretty good coating at a reasonable price.\n\nThere is an old 'tinning' plating process utilizing tin (Sn), but I think it is electrolytic and hard to put down inside a cavity like a teapot.  \n\nA silver-tin tinning "hot wash" is traditionally done inside copper pots (after acid cleaning) to provide a food-grade coating, but the teapot will have to be heated up quite hot (~200°C/400°F) to soldering temperatures, and this may play havoc with the existing silver plating, or even with the construction of the teapot (the spout may fall off).\n\nFor food-grade and chemical purity, consider some kind of polymer coating, but you'll have problems with the coating sticking, or you'll have to heat up the teapot pretty hot to cure the paint (check out "Teflon" or "Silverstone" coating services); there is a very remote possibility of an acrylic paint coating (solvent evaporation), but you'd need to know what was in the paint, or make the paint yourself.\n\nAny way you approach this problem, however, is going to run into the problem of the cost of labor - the coating material cost isn't going to the be the high cost adder (mostly because the coating is so thin).  Disposal of the plating fluids will be expensive too, so factor that into the cost as well.\n\nBy the way, you didn't say what metal was exposed - if copper, that is OK - copper pipes are used in household plumbing.  Just clean up the copper and enjoy.  Iron and aluminum is OK too, just keep everything scrubbed clean.
236563
No!  Powder Coating is electrolysis applied. The piece you are coating has a negative charge and the paint has a positive charge, it leaves little over spray, but must be baked after, The paint is vary hard and rust-proof.\nalso the process is expensive.\nThere is a spray can Epoxy paint,by Shermin-Williams, or use Hi temp engine paint, let it dry 24 hours before use.
170896
You dip the metal you want plated into a solution containing ions of the metal you want to plate with, such as chromium (chrome).  The dipped metal is attached to an electrical current, which induces a redox reaction.  The actual chemistry is a little more complicated, but the easy version is that those metal ions become solid metal attached to the electrode (the metal that you dipped in the solution).  The new metal is now permanently bonded to the old metal, and you have a set of chrome rims.
644968
One of the reasons copper was selected as the skin for the statue, as opposed to iron or steel, is that copper oxide seals the surface against further oxidation, while iron oxide (rust) is porous and continues to corrode.  That's why we can get away with copper roofs, but not iron/steel.\n\nIron, however, is much stronger structurally than copper.
254607
A metal's corrosion (rusting) rate depends on its chemical properties. Some metals just take longer than others to corrode. Keep in mind that most metals have very high melting temperature, so in general high temperature doesn't contribute to the corrosion of a piece of metal just sitting in a damp space. For temperature to be of concern, it has to be around 700 degrees Celsius.\n\nI don't know much about your experiment, but you might not be using an appropriate metal sample. Most commonly found metals come with coatings or contain chemical inhibitors to prevent corrosion. Think about bikes sitting in outside in a humid (moisture-rich) environment. Manufacturers have to coat the metals to prevent this corrosion, or else no one would buy their product. This is the case with most metals. So if you just picked up something laying around the house and tried to corrode it, your experiment might not be successful. You should also be aware that only ferrous (iron) alloys rust, and the particular metal you tested might be something else.\n\nGo to google and type "rusting metal" (without the "s). The first four sites have lots of info.\n\n*It wouldn't rust in the freezer because there's no moisture in the freezer.
548563
try Zinc.....sacrficial protection (galvanizing)\n\nyou can also use aluminium, it will react at first but then it will form a tough protective layer of aluminium oxide, which prevents further reaction....it really works
1002781
Has a plastic bonding agent to prevent the paint from breaking up and add to the reflective properties of the paint.
863380
On structures made of steel which are in constant contact with sea water (ships, oil rigs and piers) the most effective protection used is from 'sacrificial protection'. Blocks of magnesium are bolted to the structure at regular intervals and the sea water attacks the magnesium in preference to the steel. (This is because magnesium is much more reactive than iron) It is a quick method and cost effective if you imagine the labour (an amount of paint) needed to protect a large ship.
123326
Most corrosion is on the outside so it really doesn't make a difference, hot or cold. What determines corrosion is the \nenvironment outside of the pipe.