I will be resoldering a 4 inch section of top rib with 50/50 solder. Regarding the flux one book recommends zinc chloride solution, another one says rosin, and I have used nokorode paste with good results on other steel soldering though not barrel rib. Any Ideas on these or other recco's would be appreciated. Thank you.

Rosin, clean it well with a degreaser first, wire everything in place and do not get it so hot you burn the rosin.

SKB, thank you. What about using 50/50 solder with rosin core along with powdered rosin in the joints?

I use plain 50/50 solder and a liquid rosin flux. Rosin core works great for electrical connections but you need more flux for gunwork. I have no experience with powdered rosin flux so can not comment on it.
Steve

Mix the powdered rosin with acetone or denatured alcohol.

I would also wire the barrels in that area so that the heat does not travel through and melt the bottom rib solder.

Thanks Steve Mark and David. I will go with the liquid rosin flux on order now. I’ll also practice on a scrap barrel. Question, how far back from the joint should I remove the barrel blue?w

You do not need to remove the barrel blue but you need a clean surface for the solder to bond to. I usually try to de-grease the local area with acetone etc. then slip a piece of abrasive paper in the crack and try to clean it up a bit more before soldering.

I haven't had a chance to try this stuff on a rib repair job yet, but Oatey No. 95 Lead Free Tinning Flux is pretty amazing stuff. I would probably want to try it on a set of junk barrels first. It does a great job of fluxing and tinning the joint which is so important for a good job. Although intended for lead free solders, it works fantastic with common 50-50, 60-40, etc lead-tin solders. They also sell it in small tins. I first used it when I plumbed my house, and it made soldering with the lead free stuff simple and flawless. I tried it in desperation on a soldering job a couple years ago when several other fluxes failed and most of my 50-50 was rolling off and splattering on the floor. This was on a job where getting the joint perfectly clean was nearly impossible. It worked perfectly. I think it may do just as well on a shotgun rib. But I would still try to clean the repair area as good as possible with thin abrasive paper and acetone before soldering. Rubbing a graphite pencil around the repair area prevents solder from sticking to areas where you don't want it.

Thanks Keith, great tips. I have two barrels that the bottom rib is loose near the loop for about 4". I have tried soldering a small area, it held but I would like to try the longer part and like the idea of using the pencil to stop solder where you don't want it.

I would be very careful using anything but a Rosin flux. Rosin will work fine if things are clean enough. Other commonly available fluxes may perform better but they are not used in a repair application because they are very corrosive and can not be neutralized. Both Zinc Chloride and Ammonium Chloride are highly corrosive and any flux containing them would be a poor choice for rib repair. You could use an acid flux for tinning ahead of time then scrub the excess flux and neutralize.

https://www.oatey.com/ASSETS/DOCUMENTS/ITEMS/EN/No_95_Tinning_Flux.pdf

Thanks Steve that is also good to know.

Good advice for confining fluxes like the Oatey 95 to only jobs where the joint can be flushed and neutralized after tinning. Thanks for the pdf containing the chemical composition.

Thanks all for your help. I have the rosin flux and small rosebud for my oxy acetylene torch on orderand will report back when work is complete.

I would not use Oxy-acetylene.....way too much heat. Just acetylene, propane or map gas will give you the control you need. If you burn the rosin flux then you have a real problem on your hands and will need to pull the ribs completely and clean the area. The trick to using rosin flux and 50/50 is to work within the small temperature window between where solder flows on the low end and where flux burns on the high end. If you keep your work within those parameters it will go just fine. Too much heat is your enemy in this application.

I again thank those with information and encouragement. I nixed the rosebud order and was going to use the map gas torch after practicing on the old barrel. Then a good friend saw my post, he told and sent pictures of partial re soldered ribs he did with success on a fox barrel. Church bell rings and picts show very little solder clean up. My barrel is going to the fox man.

Just a question from ignorance.
Why is 50/50 solder used for ribs??
60/40 solder melts at a lower temperature and just as strong.
Maybe 50/50 is traditional and want the new solder to flow with the old.
Chuck