Galvanizing process seems to have swelled my welds

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Hello everyone.  My name is Scott and I live in Bozeman, MT.  I work in a small design studio where we primarily work with glass fiber reinforced concrete and make mostly sinks and countertops.  But we also work with a lot of steel for things like vanity bases and other furniture pieces.  I do all the welding for the shop.  Mostly self taught over the years, but have taken a 6 week course at the local vo-tech college where I learned all three processes (mig, stick, tig).  We're not building bridges, just architectural pieces for the home and business.We just recently decided to offer a galvanized finish on our steel work.  I had three large vanity bases that I probably had well over a hundred hours into the cutting, welding, grinding, and blending.  All the blends were absolutely money when they got sent out to get hot dipped to a place in Seattle.  When we received them back, all the welds that I had blended smooth were now swelled up and consequently, all the pieces look like crap.  All our pieces are sold to very high-end clients, and this is not acceptable.  Is there anything we can do in the future to ensure that this doesn't happen anymore?  I assume the heat of the galvanizing is causing this to happen.  I don't have pics now, but can take some tomorrow when I go in.  I also tried searching for the answers in the forum before I posted, but didn't find anything.  Sorry if someone has already posted about this.  Any info would help.Been a lurker for a long time, and appreciate all the advice given here.  Thanks again.
Reply:Scott in MTWelding bridges is easier than fine architectural metal.When you post your pics, give a detailed description ofyour material, fab, and weld processes.Opus
Reply:It could be a combination of several things but here is one set of considerations in the link below. http://www.galvanizeit.org/designing...e-galvanizing/ I would contact as many galvanizing pros as possible. I imagine they've had this complaint before."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:I don't know, I have never see welds reappear after they have been ground down. I have done some weld work on some part for a few peoples old cars that have been sent out to be rechromed and you can't see the welds.Last edited by mechanic416; 08-26-2012 at 01:01 PM.Reason: daawww.georgesplasmacuttershop.comPlasma Cutter and Welder Sales and Repairs--Ebay storeTec.Mo. Dealer Consumables for the PT and IPT torch's
Reply:The hot dip galvanizing process tends to warp things fabricated from sheet steel. In places like refineries, off shore platforms the sheets (deck plate) are hot dipped and bolted. Normally the bolt holes are drilled and countersunk prior to going to the galvanizer. The structural shapes (angle, tube, I beams) usually hold their shape better.For your items you might consider using stainless steel (polished) fasteners.Thanks,HoboLincoln SA200's... at least 15 - 20. They come and go. Growing partial to the "Short Hoods" in my old age. Last count on Short Hoods was 13 in possession.
Reply:Thanks for the responses.  I will take some pics tomorrow and give a better detailed explanation of the materials used.
Reply:Hot dip galvanizing is an industrial process that creates durability-not 'good looks' for high end customers. Someone made a very poor, un-informed choice in trying hot dipping.Now that you've seen how it looks, select another finish method. Do not expect consistency in the visual appearance, even if you do all kinds of additional prep prior to dipping. Expect distortion.  That in itself, should convinceyou it's not going to work for making pretty things.Hot dipping at it's best-it can and will stress relieve the weldments causing distortion, exhibit rough areas, drip edges, etc. Then there's the issues of either fully sealing tubes/pipes (burning the galvanizer, if the seal blows out) or making good, big, multiple vent/drain holes in the weldments being hot dipped.There's a slew of artsy looking powercoat finishes, plus other patina, etc. finishes that can be done consistently--with attention paid to prep before & after welding, venting/rack hanging, plugging prior to s-blast/un-plugging for racking, masking.Blackbird
Reply:Originally Posted by dave powelsonHot dip galvanizing is an industrial process that creates durability-not 'good looks' for high end customers. Someone made a very poor, un-informed choice in trying hot dipping.Now that you've seen how it looks, select another finish method. Do not expect consistency in the visual appearance, even if you do all kinds of additional prep prior to dipping. Expect distortion.  That in itself, should convinceyou it's not going to work for making pretty things.Hot dipping at it's best-it can and will stress relieve the weldments causing distortion, exhibit rough areas, drip edges, etc. Then there's the issues of either fully sealing tubes/pipes (burning the galvanizer, if the seal blows out) or making good, big, multiple vent/drain holes in the weldments being hot dipped.There's a slew of artsy looking powercoat finishes, plus other patina, etc. finishes that can be done consistently--with attention paid to prep before & after welding, venting/rack hanging, plugging prior to s-blast/un-plugging for racking, masking.
Reply:It has to do with the difference in actual metallurgy between the base metal and the filler metal.   I have yet to see any welding process used that wont do this after being hot dip galvanized.I lack the expertise to tell exactly WHY this is happening but i have observed it many many times.   It becomes very apparent when doing handrails and sending them out for hot dip galvanizing.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Originally Posted by Scott in MTDave, I appreciate your response.  We got exactly what we expected.  We knew there would be a fair amount of polishing and cleaning up to do.  We are trying something new, and after polishing, it looks cool I think.  We do all sorts of patinas, brushed finishes, sand blasting, etc.  Just expanding our horizons a little bit and trying something new.  Made plenty of drain/weep holes too.  The pieces were prepped accordingly.  Really wasn't looking for a critique of the finish, but rather a solution to the problem in my original post.
Reply:My suggestions are electro-plating galv., and then chrome plating, and then powder coat. We hot dip stuff every week. The process will give us a few surprises every now and then; mostly on thin material pieces. But most of our stuff is heavy, pipeline related, and all industrial, nothing architectural. Our only concern is that the part fit right, and be protected.Wish you luck!And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Originally Posted by Scott in MTDave, I appreciate your response.  We got exactly what we expected.  We knew there would be a fair amount of polishing and cleaning up to do.  We are trying something new, and after polishing, it looks cool I think.  We do all sorts of patinas, brushed finishes, sand blasting, etc.  Just expanding our horizons a little bit and trying something new.  Made plenty of drain/weep holes too.  The pieces were prepped accordingly.  Really wasn't looking for a critique of the finish, but rather a solution to the problem in my original post.
Reply:Scott in MT  -  I'm with Dave Powelson  -  Opus
Reply:Thank you guys for taking the time to respond.  I really do appreciate the knowledge and expertise that you are willing to share.  I apologize for not responding earlier to the thread I started, but we had a big push last week to get stuff out the door, and with the long weekend and all, I finally got a chance to sit down and respond.Here are some pics of the types of pieces that we typically produce, to give you guys a better understanding of what I'm dealing with.And here are some pics off my phone of the piece in question.I'm going to go over all the info that you guys provided to see where we go from here with this.  We talked about paying the galvanizer extra to handle our pieces as finished furniture, and not as industrial pieces.  Fortunately, the boss-man was able to get an artist friend of his in to "touch up" the spots.  Once everything was touched up and waxed, it looked good.  Unfortunately, I didn't get a chance to get any pics before everything was crated up.Again, thanks a lot for the responses and the information.  I've learned a ton from this forum and hope to be able to contribute in the future.  I'd like to revisit this thread if we continue to offer this finish in the future.  Cheers!
Reply:The two pieces in question...  The first looks real good, I see no issues.  The second photo I think shows the problem at the corner joints where the zinc coating has highlighted the welds.  It looks like alignment of the crystaline structure in the welds is different fromthat in the parent metal and this difference is reflected in the way the zinc coating cooled and crystalized on the surface.I am sorry my Dad i s no longer with us.  He was a metalurgist I am sure he would have been able to explain this phenomena and offer possible cure.  Resolving problems from A to Z is what he did.Consult with the galvy shop.  If they can't explain and offer possible resolutions you may need to seek the help of a metalurgist or metalurgical engineering firm that specializes in finish coatings on steel.- MondoMember, AWSLincoln ProMIG 140Lincoln AC TombstoneCraftsman Lathe 12 x 24 c1935Atlas MFC Horizontal MillCraftsman Commercial Lathe 12 x 36 c1970- - - I'll just keep on keepin' on.
Reply:Originally Posted by MondoThe two pieces in question...  The first looks real good, I see no issues.  The second photo I think shows the problem at the corner joints where the zinc coating has highlighted the welds.  It looks like alignment of the crystaline structure in the welds is different fromthat in the parent metal and this difference is reflected in the way the zinc coating cooled and crystalized on the surface.I am sorry my Dad i s no longer with us.  He was a metalurgist I am sure he would have been able to explain this phenomena and offer possible cure.  Resolving problems from A to Z is what he did.Consult with the galvy shop.  If they can't explain and offer possible resolutions you may need to seek the help of a metalurgist or metalurgical engineering firm that specializes in finish coatings on steel.- Mondo