MT or PT the copes before they are sent to the galvanizer. Verify that it is definitely occuring in the bath, then pay your galvanizer a visit. My experience has been that something within the galvanizing process was out of kilter when the cope cracks start showing up. I've tried gaining access to the galvanizer's bath analysis to no avail, they say that is propietary infomation and will not share. I have been told that when the percentages of tin get to a certain level that cracking is more prominent than when the tin is kept below that level. Also the temp of the pot and dwell time that the piece is within the bath seems to be relavant also. We have had cracking issues before, but only with one certain galvanizer in 35 years of working in this business. I've been told that they have since replaced thier equipment and so far we have not experienced the cracking like we have from them before. Good Luck running your problems down. I have ran into dead ends when I was looking for the causes. The galvanizer quotes an old article about how no one seems to know what causes it and sometimes it just happens. Well, I'm sorry but I don't believe that for a minute, something is causing it but no one wants to find out what that is, for some reason. [rant off]
John Wright

I have heard several times(not saying the I believe it) that the cracks are caused by the grinding of the cope.We can send 200 beams to the galvanizer and none of them come back with cracks. A month later we send 5 beams and they all come back with cracks. Then we have to use the polishing brush (as my boss calls it) which is nothing more than a grinding wheel made from 80 grit sand paper on the copes before we send the next load of beams to the galvanizer.After about a month we stop polishing the copes and try our luck agian. Sometimes we win and sometimes we lose.

Personally if I was sending material with thick flanges and webs I would make sure the copes and ratholes get grinded smooth and I would MT them, just because the amount of time it would take to fix the crack and only if the EOR would let me fix it.

I recall John's difficulties with the cracking. We too have experienced that and have never found a distinct cause for the problem. One thing that seems to aggravate the cracking is whenever pieces have been rolled, bent, or heated so that you might expect residual stresses left in the steel.
I have pictures of short (2 or 3 feet long) 10 x 10 square tubes that are completely open on the ends, that split at the ends in the bend radius. In that case, venting was definitely not the problem.
In another case some W21 beams were rolled to about a 50' radius. Those had also received some heating to fine tune the radius. Cracking was noted as radiating from the outer flanges wherever heating had occured, and also from the raised letters that Citisteel rolls into their beams.

If you have not already tried this, I would try burning your copes with a larger radius, and with the smallest torch tip that will still do a neat job. I would also be sure to grind the cope thoroughly, including breaking the edges.

Do you have the MTR's for the beams that are cracking? Have you noticed a significant difference in the chemical and mechanical properties for the beams that do crack versus the beams that do not? It might be helpful to note that; maybe it is possible to predict the liklihood of cracking.

Chet Guilford

This is a worldwide problem, a quick literature search will document problems in Germany, Japan, UK, South Africa and the United States.

A few papers

"Liquid metal assisted cracking of galvanised steelwork: A very rare but important issue" - 11/06/04
http://www.scoss.org.uk/publications/rtf/LMAC_Final_Version_3.pdf

"Galvanizing Structural Steelwork - An approach to the management of Liquid Metal Assisted Cracking" http://www.steelconstruction.org/steelconstruction/view?entityID=107&entityName=publication&jsp=source&sessionID=-1132669845955

The following is the link to the report from Mr. Tom Kinstler that was produced with help from AISC.
http://www.aisc.org/Template.cfm?Section=Technical_Answers&template=/ContentManagement/ContentDisplay.cfm&ContentID=30636

Along with the Summer 2004 Inspection Trends article "Inspection for Galvanization-Related Cracking in Steel Structures"

Tin, Bismuth and other low-melting points elements in the galvanizing bath do play a role in Liquid Metal Embrittlemnt or Liquid Metal Assisted Cracking.

From the Fall 2005 Inspection trends article -
"The presences of low melting point elements such as Tin and Bismuth, in the galvanizing melt have a role in causing LME.  However, the relative significance of melt-composition in the galvanizing bath on the potential for steel cracking is not fully understood. 

The inspector should always obtain a copy of the bath analysis, looking at the Tin, Bismuth and Lead level. SEM and XDS analysis of the crack surfaces have indicated high concentrations of these elements in the cracks.  If the %Tin (wt) + % Lead (wt) is greater than 1.3% (by weight) or the %Bismuth (wt) is greater than  0.1% (by weight) a closer examination for cracking is warranted, preferable with Dry AC Yoke  MT."

A literature search will reveal that cracking due to liquid metal embrittlement during galvanizing of steel, has been known since at least the 1930s. Known only as an occasional minor problem, until recently. During the past decade, galvanizers have increased their kettle size allowing larger items to be dipped as a single piece. As these assemblies have increased in size and complexity so have the occurrences of LME increased. In the mid 2002 several cracks were visible observed in a newly erected galvanized truss bridges. The crack surfaces observed were coated with the galvanizing alloy. To determine if additional cracking had occurred several non-destructive examinations methods were evaluated. By employing the common, low cost NDE method of AC yoke magnetic particle inspection yielded the observation of many additional hidden cracks.  A key paradigm of cracks is they never heal themselves nor go away, but continue to increase in size over time, eventually growing large enough to cause a failure.  Complex assemblies, like road sign structures, roof trusses, communication towers and bridges, all share the three ingredients for a hidden LME crack to occur; stress, liquid metal contact and material susceptibility. 

Since there is a potential for a catastrophic failure to occur with a galvanized structure, methods to locate the discontinuities are required. Current, traditional technologies include: Visual, Magnetic Particle, Ultrasonics, manual and automated Shear Wave, and Phased Array UT, Eddy current and ACFM Alternating Current Field Measurement. Out of these Magnet Partcile MT and ACFM  Alternating Current Field Measurement work the best to uncover these defects/discontinuities.

In a fabrication shop the assemblies should be inspected prior to galvanizing, as per many of the fabrication codes and specifications that currently exist, i.e. direct observation of the welds and base material. However, these same codes do not require and inspection, sans  cosmetic appearance following Galvanizing.

Discontinuities that could result in a catastrophic failure may be hidden beneath the galvanized coatings in complex assemblies.   If a failure were to occur in these assembles, the failure could result in the loss of life and property. In the UK cracks in a galvanized structure were observed after four years of service during an annual inspection when the crack grow and broke the surface this resulted in the replacement of the structure. In the US a bridge was repaired after two years of service when a crack was observed.  In Germany a new parking garage showed many cope cracks and had to be replaced.  Prof Sedlacek, at al, in Germany has investigated LME and Cope Cracking of Hot Dipped Steel Beams associated with a parking garage.
"Zum Feuerverzinken von Stahlkonstruktionen - Ursachen und Lösungsvorschläge zum Problem der Rißbildung " http://www3.interscience.wiley.com/cgi-bin/jissue/110456644   
"Zur sicheren Anwendung feuerverzinkter Stahlträger" http://www3.interscience.wiley.com/cgi-bin/jissue/109568359
"Reliable application of hot dipped zinc coating of steel beams"

In all these cases the crack surfaces were covered with material from galvanizing (zinc, tin, bismuth, aluminium ...).  

If you have the MTR's calculate the the Carbon Equivalent in Zinc for Valid for Carbon < 0.12%

CEZ  CEZ=  C + Si/17 + Mn/7.5 + Cr/4.5 + Cu/13 + Ni/17 + Mo/3.0 + V/1.5 + Nb/2 + Ti/4.5 + 420B === <0.44

CEZ should be less tan or equal to 0.44

I am a firm believe that a bath analysis is required, and should be given to the customer. However with the ASTM Committee A05 on Metallic-Coated Iron and Steel Products consists of many galvaniziers that are opposed to this. Many State DOT's are now requiring a bath analysis, so this might change.

edit" added url tags so that the links are now clickable-JW

We too have had this problem in the past. Search this site for previous discussions on the subject. Mr. Beldyk has been great at getting me information on this in the past. If it works well into your job delivery schedule and to help the industry research this, document with photos and conditions all cracks and forward them to Mr. Beldyk and AISC. Start to document during fabrication and before galvanizing. We too have polished radii to fine finish and a good radius and still had cracks. It is frustrating to spend excess time and still have cracks.

Repairing these cracks was performed by gouging and/or grinding along the crack to 2/3 to 3/4 of the way through the thickness of the member and past the end of the crack (D1.1 says 2" past), removing zinc within at least 1" away from weld and welding up that side with a low hydrogen process. Treat it as a CJP weld. Turning the member over and repeating the process. Assure you have removed the crack with MT. Repair the galvanized as you normally would damaged galvanizing.