Technical Any tips on filling in pitting on frame with brazing rod?

I’m trying to fill in some heavy pitting on an area of a frame (front cross member) using some brazing rod. There is quite a large area with minor pitting, and it is proving a bit difficult to get the material to flow easily. I’ve sand blasted the area yesterday, so it was clean. Initially, I used my hearing tip thinking it would introduce less heat, but a section still got warped. Today I switched to a #2 tip which offers much better control of the heated area and puddle. There is also some pitting on the vertical surface which is also a challenge, but I have managed to get the braze material to stick without pooling into globs. The area which was previously warped, warped even more (long narrow low spot), and I’ve been adding more material to level it out which to have seemed to work. I think this area must be really thin from corrosion which caused it to warp like that. So far, I’ve gone through 4 rods and am wondering if there are tips folks can share. The reason I’m doing this is the owner of the shop which is going to blast and paint the frame said I couldn’t repair this area up front with body filler as it wouldn’t take the heat from his oven. He also won’t do any type of work to fill in the pitting. He will use epoxy primer and a top coat which I’m guessing will fill in most of the minor pitting. Is that correct?

 

Why use brass? Are you gonna finish it good enough to powder coat. Myself I’d stir up some brand of epoxy.

 

This is paint? What kind of oven is he using to cure paint?

There is a company in Ontario that makes a filler for powder coating. The company is Tiger Coatings and the filler is EPO-strong. It will with stand heats up to 400 F. You might try them. They are in Guelph.

 

While I love to braze, for this job I would use a mig welder or a stick welder with a very small rod. Tig would be best, but I don’t have one. Just my thoughts.






Bones

 

I have filled HD frames with Liquid Steel and had them power coated with no problems.

 

Sorry, it will be powder coated along with my rims, axles, etc. Thanks @K13, I’ll look into their product. Frame will be going in 3-4 was to the shop.

 

The only issue I see with brass is getting everything clean after you lay the brass on and do the finish work. You have to do the right steps to get rid of the acid you use to prep the area.
Powder coating just like paint doesn't hide or fill anything, If anything it makes flaws show up more.
Other than that I would go with what you are most comfortable working with be it steel or brass with a torch, Mig or Tig. Or possibly what you have available in your garage to use. Not everyone has a Tig and a lot of guys may not have a mig welder.

 

I have brazed and molded HD frames but it was easier to position the frame as level as possible to allow the braze to flow better. The most crucial thing is achieving optimal temperature control.
Today there are better ways. I don't have any personal experience but have heard about epoxy fillers with conductive metal that are used for powder coating. Maybe look into that.

 

Lead

 

Use body lead. You won't even turn color on the base metal to apply it. No warpage. You will have to paddle it on the vertical areas.

 

I have yet to find a non-metal filler that doesn't show seams after powdercoating in some degree. The problem seems to be the different expansion rate between the base metal and the filler. Size of the area and filler thickness will effect the final results. You can reduce this to near-invisibility by multiple coats at the problem area and block sanding between coats but that's time consuming, and getting the coaters cooperation may be tough.

The other major problem is if the coater sandblasts the repaired area for good 'tooth' for the powder to stick to, that will erode the filler (and this includes brazing if aggressively blasted). Solder (and possibly body lead) will 'move' at cure temps, I had zero luck trying that.

I'd replace the offending areas personally if you're determined to have powder, or barring that, maybe fabricate a sheet metal cover to go over it. Or just bondo it and paint, that will be the easiest solution. A good quality paint will be nearly as durable and much easier to work with in this case.

Powdercoat is great stuff, but this is it's major limitation.

 

Sounds like you need to cut it out and replace that area or the whole thing. Crossmembers are for strength and hiding flaws is not going to make it strong again.

 

I would agree that knowing what I know now, replacing the affected area would be the correct 100% solution, but at this point, I’m goong to leave it as is. The affected area (warped /low spot) is about 1” x 4”. It probably has already between 1/16” - 3/32” thickness of braze material added to make it level with the surrounding area. I’m hoping this will be sufficient to mimic the original integrity. The cross member is fully boxed and the affected area is next to the metal overlap of the two pieces making up the cross member. Additionally, the original bumper encases the top and bottom of the cross member. This is was caused the corrosion in the first place.
Now back to my question. I actually decided to braze based on an earlier interweeb search that brought me to a thread here on the HAMB. Most folks akso said the same as I’m hearing here. Because of the heat used in powder costing, most if not all of the typical approaches aren’t really viable. Even the stuff from Tiger Costing seems to be very installation specific down to using their own powder coating. The one comment that stuck in my head from the thread I came across in my search was one about a guy who either worked with or knew someone who worked for a high restoration shop. He said that for muesum type vehicles they would use braze material to fill in voids left by corrosion.
I haven’t yet had a chance to dress the latest application of braze material, but I felt much more confident in what I was able to lay down. We’ll see, but I took this as an opportunity to learn a new skill set as I feel this type of metal work is becoming a lost art.

 

Where did you get the info that EPO Strong was specific to their powders? I have had a bunch of customers use it with no issues.

 

Bingo! Surprised the early posters didn’t advise this.

Ray

 

A front cross member is a structural component of a chassis. I would be
concerned about the strength of this member if it rusted that badly?
Perhaps it should be more closely evaluated and replaced or replicated.

 

I have used JB Weld 24 hour cure for a lot of projects that were powdered coated with great success.
Vic

 

The hardest part of brazing is getting paint to stick to it. This has been discussed here before, I'm sure someone can dig it up.

 

We metal plasma spray badly pitted areas and grind back flush. Most larger cities have this service which is used a lot in machine shaft build up. I tried it on floor pans with holes (had to use backing) but not satisfied with results.

 

From the way I interpret their “Limitations” statement, they want you to use their powder coat. They also mention requirement for forced cure, or 2-3 day cure at ambient. They also mention ygat the putty should be polished. Not sure what that means. I have no doubt that it works, and perhaps even JB Weld, but I doubt shop will accomodate any “special instructions”. Trying to get in touch to see what owner has to say, but no luck. I didn’t know painting a braze material might be a problem. I’ll need to confirm with shop.
Again, I appreciate all the feedback, but I was really hoping for some actual tips on “repairing” the pitted areas using a brazing technique.

 

In Street Rodder mag Professor Hammer suggested tinning with lead over brass as
the paint would not adhere to the brassing, (spelling may be off).

 

Sound like someone is asking for permission to do a half ass job.

 

Gave a quick pass over with a flap disc this morning, and noticed the cross member is now about 1/8”bowed in two directions. This has now gone from bad to worse. Damn! Going to try to pull it out with the winch on my truck using a bit of heat as well. Although I have practically zero experience brazing, I’m really surprised at how much the cross member had warped. It looks to be about 3/32” in thickness. I will call the metal shop tomorrow to see how quickly they can bend me up a section so I can replace the affected area.

 

Ziggster, don't wish to belabor the point but will take one last shot at it. The problem is ALSO that this component is going to have rust inside of it that is going to continue working on the brace. Its good that you learned how to braze. Chalk that up as a positive and something new to your arsenal for future use. I would also accept the chance to learn that sometimes its best to realize something is not working as well as one hoped and that a different path is better. Not only are you going to possibly have coating issues initially........they may rear their head later. Rust never sleeps even if its where you don't see it. In the long run you will have fewer problems if you just get a replacement part and install it. I mean this to be helpful, so please take it that way. Good luck whatever you decide...........

 

Yep, no offense taken. As mentioned in my previous post, I’m going to look into getting a patch made. I’ll just try to straighten it out a bit first.

 

The 11 ga patch panel should be ready this Friday. Also spoke to the powder coat shop owner. He said that he has had lead based solder melt when doing fuel tanks. Not sure if that is the same as body lead. He thought it would probably melt. Said oven temps are between 400F - 450F. He also said having braze material is fine as the epoxy primer sticks and the powder goes over.

 

Cut out the affected section. It was actually pretty bad and had “caved in” about a 1/4” from the heat. It is no wonder that I had to keep adding more braze material. Thanks guys for pushing me to do the right thing. The stuff inside the frame is sand from the pressure wash sand blast attachment.

 

Got it welded in yesterday afternoon. Patch panel wasn’t exactly 90 degrees at one end, so a bit tricky to get it to line up with the two surfaces. Will finish it off today. Frame is being picked up on Friday.

All welded in. Added hole like original but couldn’t tadius it.


After first pass with flap disc and some extra welding to fill in some of the uneveness.