what are the defect of hot dip galvanization?
90066
Uneven coating thickness, voids where the surface was not clean or properly treated. You can also get bubbles, if the zinc is not skimmed for dross. Electroplate is more expensive but nicer, smoother finish. Hot dip is fine for most things, hardware, etc. But a large enough item might cool the hot dip bath and then it would not take to the surface, which could lead to peeling.
529301
test the corrosive properties of different solutions. Use ungalvinized steel nuts from hardware store. ( It is important that they are not galvinized, not stainless, and not zinc.) use soda, salt water, tap water, urine, bleach, and vinegar. It should yeild surprising and interesting results.\nP.S. don't use metal bowls, take lots of pictures.
1123947
Was the glass heatproof or pyrex? Probably the rapid heating caused the problem, not the salt water directly.
598430
Copper has a higher melting and boiling point and better electrical conductivity.\n\nIf you are a die caster, Zinc would be better because it can be easily pressure die-cast and hence better accuracy in the cast component with minimal metal removal for finishing.
874237
R&D Projects\nAdvanced Computations\n\n \n\nAlloy Selection System for Elevated Temperatures (ASSET)\n \nMany aspects of equipment design and operation as well as alloy selection and design are influenced by the expected lifetimes of equipment in high-temperature, corrosive gases.  Currently, many processes are limited by the inability to predict corrosion rates for equipment used in high-temperature processes. A new database is being developed to enhance the ability of the chemical industry to predict corrosion of commercial alloys.  Benefits in improving the ability to manage corrosion data for alloys in high temperature, corrosive gases will be far reaching in the chemical industry.   Better characterization of alloys under operating conditions will result in reduced energy use and maintenance, increased process safety, cost-effective use of expensive alloys in equipment designs, and improved productivity.   \n\nASSET will be an alloy selection and corrosion prediction system that includes a database linked to thermomechanical calculation programs.  The linked programs will use experimentally measured corrosion data obtained under well-controlled conditions to predict the corrosion rates for commercial alloys.   This project will include data on an extensive list of alloys exposed to a wide range of complex and corrosion gases for temperatures of 250 to 1,150oC.  The considerations being used to generate the corrosion data include oxidation, sulfidation, sulfidation/oxygenation and carburization.  The approach to this project includes improving and expanding the ASSET system and training participating companies in its use.
627053
It actually depends on the system material and the media. The galvanizing process uses zinc as a primary element. Most annodes are... zinc. Any system that is cathodically protected by a zinc annode would most likely attack the galvanized finish of the pipe.
161637
ionic,the diference in electronegativity values is greater then 1.6.  the metal bonded to a non metal method is also correct
796939
Process Issue.\n\nThe Metal prior to Plating must be free of all contaminants.\n\nHave the Process and quality staff examine the Brass prior to the Plating and do a Controlled experiment with a sample size run.\n\nPerhaps a contaminate is entering the Process at a stage in the Handling of the Brass.\n\nProcess control must be verifiable at all times.\n\nClosing down the Line is costly and very expensive. But, The Product that the customer receives must be defect free.\n\nPlease review the following URL:\n\nhttp://www.finishing.com/96/76.shtml\n\nContact me by email, if I can offer addition assistance.\n\n\nRegards.
1185511
There are many different methods, but basically it is a form of preventing or slowing a chemical reaction between metals and air or other impurities. Eg. Painting, plastic dip coating, anodising.\n\n“Corrosion: A partial or complete wearing away, dissolving, or softening of any substance by chemical or electrochemical reaction with its environment. The term corrosion specifically applies to the gradual action of natural agents, such as air or salt water, on metals”.\n\nAlso Fretting corosion:\nFretting corrosion refers to corrosion damage at the asperities? of contact surfaces. This damage is caused under load and in the company of repeated relative surface motion, as induced for example by vibration\nOther causes:\n• corrosive environment\n• contact load\n• amplitude and frequency of load fluctuations\n• cycles\n• temperature\n• availability of moisture\n\nPrevention for fretting Corrosion: \n• Use of lubricants and surface coatings designed to improve lubricity and limit metal-on-metal wear. \n• Increased surface hardness. \n• Use of barriers to limit ingress of corrosive environment to mating surfaces. \n• Reduce bearing loads on mating surfaces.
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.
237301
Welding on galvanized metal can be dangerous.  The best bet is supplied air.  This would be preferable over any filter. Always make sure there is good ventilation, too.
1145145
Dissolved materials that can precipitate out of solution can cause problems with appliances. They are a particular problem with systems that heat water, because this increases precipitation and causes scale. This can reduce efficiency of heating elements, and can block pipes.\n\nHeating systems suffer less, because it is always the same water, so once the solids have deposited out there are no more to add to the scale, and this is very little scale. However, other dissolved materials can cause problems by leading to corrosion.
1038988
You need to look up ASTM A120. That is the standard for galvanized pipe.
211196
I doubt if I can list ALL the defects possible in metal castings, but here are some of the more common ones.\n\n1.) Hairline cracks\n2.) Bubbles caused by water vapor\n3.) Alloy proportions wrong\n4.) Defect in sand mold causes blemish
524355
I'm a metallurgist - weld material is more highly 'strained' than the parent material, so it is more prone to acidic corrosion relative to the parent material.\n\nThere is another possibility:  how do know the "weld metal" was the same as the parent material?  Perhaps the weld material was had fewer alloying elements so corroded sooner...  (cheap filler metal)\n\nOne more thing to consider:  if the part was hooked up to any electrical source, the corrosion could be caused by electrolysis rather than acidic corrosion (no kidding! happens more than you think).  Check with a voltmeter to ground; I've had batteries just eat right through stainless over a weekend; if so, insulate!
327609
If I've understood what you're asking then:\nA\nCd(s) + Ag2+ -> Cd2+ + Ag(s) \n\nCadmium occurs at Anode and the Silver would deposit on the Cathode\n\nB (I hate Manganese equations and the partial above is incorrect)\n\nMnO2 + 4H+ + 2AgBr -> Mn2+ 2Br- + 2Ag + 2H2O\n\nMnO2 @ Anode\nAgBr @ Cathode\n\nC\n\n(PtCl4)2- + 4Ag -> Pt + 4AgCl \nAg @ anode\n(PtCl4)2- @ Cathode
302323
Although the type of corrosion most of us are familiar with involves molecular oxygen, corrosion, in general, does *NOT* require the presence of free oxygen.  \n\nFor example, galvanic corrosion, which can occur when two dissimilar metals with different oxidation potentials are in electrical contact.  The less noble metal will form an anode, and be oxidized, while the more noble metal will form a cathode, where reduction reactions will occur.  In the absence of oxygen, reduction reactions like:\n\n  2H+ * 2e- -> H2(gas)\n\ncan occur.  This reaction is particularly important in acidic environments, (when the H+ concentration is high).  Such environments can develop in corrosion environments via hydrolysis reactions, e.g., \n\n  Fe3+ + 3H2O -> Fe(OH)3(solid) + 3H+\n\nwhere the Fe3+ ions are produced by the oxidation of iron metal, and Fe(OH)3 is the solid mineral "goethite", a major component of "rust".\n\nCorrosion can also be induced in the absence of free oxygen by the action of some species of bacteria. For example, there are bacteria that can reduce sulfate ions (SO4--) or nitrate ions (NO3-) to hydrogen sulfide (or metal sulfides) and molecular nitrogen.  To do so, they need to couple these reactions to a "source" of electrons, which can be a metal surface that is then oxidized (i.e., corroded). \n\n\nFinally, there are some metals that are themselves strong reductants -- so strong that they can reduce water.  Li, Mg, Na, and Al all have standard oxidation potentials that are lower than that of water, so they will react spontaneously (in the case of Li and Na, *violently*) with pure water (even water containing no free oxygen) to form metal ions or hydroxides and hydrogen gas.