zinc oxide coating on filler???

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I have contracted a job welding 7"Lx0.5"D round stock to 0.250 flat stock with thru bore. A basic 0.5+ button weld. The fisnished product is to be chem coated. The shop owner expressed to me that there were problems with the past welding contractors, one being scale left on weld, causing the coating to flake off. Attempting to remedy this, he changed coating from black oxide to black zinc chromate. Due to changes in welding apl, the coating would not adhere. Confuses me too. Anyway, both the shaft and plates are 1018 carbon. The shop owner asked if I could use the same,(1018), as filler when welding,  to avoid past coating problems. The carbon filler rod I'm using,(tig), is ER70-s. In the past, I have sanded the copper/sili coating off filler prior to welding 100% x-ray. My Questions to all ya'll gooroos is will that work for this job, and\or is 1018 carbon filler available????Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:1018 filler... would be no different to autogenous welds, from a weld chemistry point of view. Porosity likely as ERxx fillers contain 'deoxidisers' (silicon, aluminium, manganese) to deal with any oxides present. It would be easy enough to confirm this yourself- shear a strip of 1018 from a sheet to use as filler70s-2    0.1C 0.6Si 1.3Mn 0.2Al70s-6    0.1C 0.3Si 1.3MnFrom what you said, sounds like the problems were caused by the previous welder/ whoever is applying the coating- how could anyone expect any coating (paint/powdercoat/plating etc) to adhere to a part that has scale on it . If the weld process was TIG previously then there shouldn't be any scale/surface smut anyway
Reply:Change the process to coat after welding.There is no "scale" on a weld bead after welding, especially with GTAW.  There could be silicon islands if you use a high-silicon containing filler like an S-6.  But that should be able to be removed by the post-welding clean-up procedures like wire-brushing and pickling, etc.  If silicon islands after welding are a problem, then try an S-2 filler (ER70S-2) instead of the ER70S-6.Let's see if I understand.  You have 1018 1/2 " OD rods and some 1018 1/4" thick plates with 1/2" diameter holes through them.  Your job is to weld the bar and the plate together.  You are using GTAW as the welding process.Clean the parts of oil/grease/gunk, grind/sand/machine any bevels needed for welding, clean again, weld.  Send to inspection, then off to the coating steps (clean, wash, pickle, coat, etc).  The best laid schemes ... Gang oft agley ...
Reply:Sounds to me like they used to perform the welds without grinding the original mill scale off of the base material.  If it were clean, the chemistry would be so close with almost any mild steel filler material that I don't see how there could have been an adhesion issue just in the welded area.
Reply:Thank ya'll for all the good info.. I welded a few test pieces, using E70S-2 filler to confirm that the fixture I fabed was with in tolerance, +/- 0.5 degree, I'm going to request the customer to have test pieces coated to confirm adhesion before I start production on the 2400 pieces. From visual inspection, I don't expect any problems.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Maybe the coating was misapplied after the change to chromate; it may have not been the first welder's fault there. I also don't know why the filler alloys would have any effect on either coatings; both the silicon and manganese levels are reduced by dilution and oxidation, and shouldn't be high enough to begin with, to have any effect for the processes I've read about---but I must admit I've never worked in the field so don't quote me!We/I could use some before and after pictures, just out of curiosity if nothing else. Do you know what the parts are for or go into?
Reply:the parts are mounting brackets involved in the break-away mec. in commercial auto-opening slide doors. The doors at the grocery store for example. I will post pics in a few days.      Thank ya'll for the info.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:I've done a bit of work with chromate conversion coatings in the past.  I second the notion that the coating failure your customer experienced is most likely due to inadequate cleaning of the parts prior to coating.  Zinc chromate coatings need to be applied to a clean, oil free surface.  If your customer has you(or the previous fab shop) apply any kind of rust preventative(solvent or water borne) to the parts, be certain to remind the coating shop that they need to clean prior to coating.  If they don't, problems are sure to follow.  Depending on the surface texture of the weldment, and the cleaning process used, I can easily imagine bead ripples retaining more oil or contamination.  This would tend to make the coating adhesion worse overtop the bead, as compared to the surrounding smooth flat surfaces of the plate and rod.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:Here are pics of the jig I made to hold squareness and shaft length. I'm having trouble doing the button welds,(tigging), and keeping the finish button uniform, without applying too much heat. Maybe I need to break down a buy a mig??? Attached ImagesMiller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:Slightly 'overfill' the weld bead, then grind/mill/machine flush.  Done.  Send to the plating/coating shop.Probably overkill to grind/mill the weld though, unless there is a dimensional tolerance or dimension that has to be met for the plate.If no dimension issue has to be met or considered for the weld bead, a quick pass with a powered wire brush should take care of any silicon islands in the weld surface.  Or a quick blast from a media (aka 'sand' blaster), but the plater/coater still has to make sure that the parts are clean enough for the plating/coating.Hmmm, or maybe a quick tumble in a vibratory cleaner/polisher with the appropriate media.Speed of weld applied - use MIG.  More precision of the arc - use TIG.  Your call as either should work just fine for your application.If there is a coating failure or issue, I still think it is in the steps (or lack of steps!) done by the coating/plating shop.  The best laid schemes ... Gang oft agley ...
Reply:the weldment has tolerances of: 3/4" max weld diameter- 3/32" weld heigth- 1/8" min. penatration, and needs to be somewhat smooth for coating, and no under cut.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180
Reply:How much oxide do you get on the underside? I would expect very little. Could the previous welder have been using OA? Getting scale left on the surface? After seeing the parts and all, I still don't think that your using ER-70-s-6 with the higher level of deoxidizers, or leaving the copper coating on, would have any effect on the coating. I would expect the plater to be able to (and responsible for) chemically remove any slight surface oxidation before applying the chromate, as part of the cleaning operation.How long does it take to refill the jig as compared to do the actual welding? How many parts are to be welded and do you have to do them all at one time, or is the work spread out over weeks?
Reply:Originally Posted by Oldiron2How much oxide do you get on the underside? I would expect very little. Could the previous welder have been using OA? Getting scale left on the surface? After seeing the parts and all, I still don't think that your using ER-70-s-6 with the higher level of deoxidizers, or leaving the copper coating on, would have any effect on the coating. I would expect the plater to be able to (and responsible for) chemically remove any slight surface oxidation before applying the chromate, as part of the cleaning operation.How long does it take to refill the jig as compared to do the actual welding? How many parts are to be welded and do you have to do them all at one time, or is the work spread out over weeks?
Reply:I fixed the final appearence of the button welds, due to excessive heat.I purchased a foot pedal for my maxstar, also some 5/32 E-70-S2 filler, welds look much better.Miller TrailBlazer 251Miller HF-250-1Miller MaxStar 150 STLHyperTherm PowerMax 380 plasmaLincoln PowerMig 180Millermatic 252Miller Diversion 180