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Letter 34079 Galvanized vs. electroplated bolts, nuts and washers+++++ Dear sir, We have to supply some fabricated structural members along with fasteners.The client's specification for the fasteners says that HM 8.8 BOLTS, NUTS AND WASHER-Galvanized. This instance could I supply these fasteners which has been galvanised by electroplating method? And please advice what is the difference between the hot dip and electroplated. Thanking you Velayudham Ravishankar
+++++ Hot-dip galvanized coatings are far heavier than electroplated zinc and will exhibit greater corrosion resistance, Velayudham. It is never permissible to make a substitution without approval, however, because one never knows the intent of the specifier. For example, zinc electroplating is also susceptible to whiskering whereas galvanized coatings are not believed to be. If these items are intended for a computer room, you could have great liability. Regards,
+++++ I agree with Ted. Hot Dip coatings are usually thicker, better bonded and will probably perform better than electroplated zinc, which are commonly more used for cosmetic purposes only. We find these fasteners are only well protected in stored conditions. For structurable fabrications, if atmospheric corrosion is your concern, I would get the client to agree on a design change. But does it ever actually rain in Bahrain? Martin Rich
+++++ Is it really the case that electroplated zinc coating is mostly cosmetic? Would you also offer your opinions on fasteners in ACQ-treated wood in outdoor structures? Does the particular copper-rich formula of ACQ accelerate corrosion of galvanized nails, screws, and bolts? I use 1/4" to 3/4" diameter bolts, mostly 3/8". I use either hot-dipped or electroplated zinc bolts. Should I not use electroplated any more? Thanks. Michael Cohen
+++++ Zinc plating is fine for some applications, Michael, mostly indoors -- but it's corrosion resistance isn't enough for rough outdoor service. The ACQ manufacturers have highly specific recommendations about fasteners but, yes, copper in the wood will accelerate corrosion due to the galvanic couple.
+++++ Mr Ravishanker Hot dip galvanising puts a thick zinc layer all over the part and does protect well. There are Electro Galvanising ( electroplated ) Zinc iron alloys that perform very well and compete with Hot dip galvanised coatings for Corrosion resistance. These bear a look . Regards,
June 4, 2006 I HAVE RECEIVED SOME 3 METER CHANNEL CROSS ARM WHICH IS ELECTRO GALVANISED. DUE TO HEAVY RAIN IT IS GETTING CORRODED. WHAT MEASURE I HAVE TO TAKE FOR STOPPING CORROSION AND ANY ZINC SPRAY WILL HELP TO STOP THE CORROSION. IS ELECTRO GALVANISED OR HOT DIP GALVANISED GETS CORRODED FAST. AWAITING YOUR EARLY REPLY WITH SOLUTION TO RECTIFY THE DEFECT. N.JAYAKUMAR
October 18, 2006 I'm under the impression that the thickness of the zinc coating is based on the standard or procedures for the specific galvanizing process. For example, a hot dipped galvanized piece could be galvanized to a lesser zinc coating thickness than an electrogalvanized piece. (Typically not the case, but as an example.) Are my assumptions correct? I've spent a little time researching this...Also, the thickness of the steel must have an effect on the thickness of the zinc coating, right? Is or are there any studies or information documenting this? David Riley
October 17, 2006 Hi, David. The thickness of electroplated zinc on hardware is typically controlled at anywhere from from .0002" on up to .0006" according to specific needs. The upper limit is usually based on practicality in that it takes over an hour of zinc plating time to reach .0006" in barrel plating and it becomes uneconomic. There is no real lower limit, but the sloppy and dangerous "specification" of "commercial zinc plating" is often interpreted to mean .0002". The thickness of the steel has no effect on the thickness of electroplated coatings. Galvanizing is never that thin. Typical thicknesses are .0015" to almost .004". In general you can't really control the thickness; rather it depends on the surface condition of the steel. Thicker steel takes longer to heat up and usually takes a heavier coating. In all, it might barely be theoretically possible for an exceptionally thick electrodeposited zinc coating to be as thick as a very thin hot dipped coating, but it is essentially unheard of. Rather, a "rule of thumb" might be that galvanizing is about 10x as thick.
July 25, 2007 Can we use electroplated Binding wires for construction purpose or is it better to use hot dipped only??? Prasad A. Haridas
What is the difference between Galvanised Iron and hot dip galvanised iron. Are both the same or electroplated iron is called as GI ? Syed Mohamed Gani Gani
May 27, 2008 Hi, Syed. The phrase "electrogalvanized", which means zinc electroplated, has become common pretty common usage. But to my mind GI means "galvanized iron" and "galvanized" means hot dipped. Unfortunately, it's hard to put a fine point on words like this. Because although I can say "electroplated" is not "galvanized", a supplier of the electroplated finish can always say "I've always called it galvanized; try to stop me!" Regards,
June 25, 2008 Hello Ted, Reinhold Becker
June 25, 2008 Hi, Reinhold. Sorry but I have no idea what production, if any, China will be halting during the Olympics. But here in the USA, and probably in Germany as well, it has been many years since an electroplating plant has been permitted to pollute. It is often difficult or impossible to calculate the environmental impact of one process against any other. So I would turn the question around and ask the person who claims that electroplating is more polluting than galvanizing to present any calculation whatsoever to promote his case and give me a shot at tearing it apart. In the best light most such claims are based on highly subjective and transient interpretations of environmental impact. Regards,
July 1, 2008 Hi Ted, thanks for your reply. Surely there are, as you mentioned,
many points of view "what is polution" ( in general speaking)and what
kind, style of polution we talk about. I was just hoping it was easy
to get get a reply like " method A is clearly considdered to be more
harmfull because of ..... Therefore method B came into the picture"
Best regards from Hamburg Reinhold Becker
July 2, 2008 Can you give me a URL for a news report about this? As I say, I haven't heard anything about any shutdown at all, let alone one targeted specifically against electroplaters. And I don't know who "they" are who claim that electroplating pollutes more than galvanizing, let alone what parameters they use in making such a claim. I don't think method G came into existence as a result of pollution or perceived pollution by method E (they've both been around for over a hundred years) so I can't enunciate the relevant list of alleged pollution grievances :-) But rather than belabor the point, I will say that E is a "wet process". Ions of the metal to be electroplated are dissolved into aqueous solution, and those ions are washed off with water. That introduces the potential of discharging water that may contain an excessive amount of the metal in question. Regards,
July 16, 2008 Hello Ted, Reinhold Becker
July , 2008 Hi, Reinhold. I saw mention of "coal mines, coal-fired power plants, steel mills, cement factories and other clusters of heavy industry" and "coking operations, cement factories and small power generators", but not electroplating or galvanizing. No metal is released into the atmosphere by zinc electroplating or galvanzing, and it is relatively easy and inexpensive to scrub the acid and alkali fumes, si I doubt that either contributes substantially to air pollution. Regards,
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