Graphite Resist in Soldering...

[RoughboyModelworks]

I'm presenting this SBS in response to a request from Michael Mott in Marty's Corliss thread. I thought it better to start a new thread rather than hijack Marty's. The actual technique is really very simple. It's a lot harder it seems to get consistently good photographs of each step. I'm not particularly happy with the photographs, it's taken most of the weekend to get these. Part of the problem is I'm using mixed temperature light sources, but unfortunately at the moment I have no other option, so the colours are a little off but hopefully you'll get the idea.

For the demonstration I used a couple of pieces of brass from the scrap box, a piece of flat stock and a piece of "T" stock. The raw pieces are shown below:



The first step in preparing any pieces for soldering is to clean the mating surfaces. For this purpose I use Carr's Acidip, which removes any oils or grease from the surface and micro-etches it.



After fluxing the piece of "T" stock, I tinned it with a layer of solder. The important point to remember in any soldering operation is to not use too much solder. More solder does not make for a stronger joint, just a sloppier one with more cleanup needed later. For this demonstration, I purposely tried to make a sloppy joint, to better demonstrate the effectiveness of the process, so tinned this part with a little excess solder.



The next step is to apply the graphite resist or barrier. With the "T" section in position, I painted a line of NeoLube graphite onto the flat stock. NeoLube is a dry film industrial lubricant composed of a very fine graphite in isopropanol. It dries in a matter of seconds after being painted on a surface, leaving a graphite film. I painted it only on one side and end in order to show the effectiveness of the technique, leaving the other side and end plain. Normally you would surround the entire joint. This technique is particularly useful when soldering piping or fittings into holes in boilers or other surfaces. You simply paint a ring of graphite round the opening. You can also use an HB pencil for this purpose, which works reasonably well for ringing holes with graphite, but I've found NeoLube to be the most effective material to use and the easiest to see in a SBS.



With the resist in place, flux is added to the opposing faces of the joint (taking care not to flux away the graphite) and the pieces were sweat-soldered together.



The picture below shows the assembly immediately after soldering. You can see the graphite resist on the near side and end, while on the opposite side you can see where flux and solder have flowed out from the joint onto the bare brass. There is also more discoloration of the brass on the unprotected side. Following a quick and simple cleaning with denatured alcohol to remove any remaining graphite and flux, we end up with the piece as shown below. It's readily apparent that the graphite side is much cleaner than the opposite.



Any remaining traces of graphite and flux will be removed in subsequent operations prior to painting, specifically bead blasting as can be seen in the last photo. The left side in this shot is the graphite side which is almost perfectly clean while the right side has a smear of solder.



Viewed in a single instance, such as in this demonstration, it may not appear like a particularly useful technique. But used throughout construction of a complex project, it can save a lot of time and effort in solder cleanup.

Paul

[marc_reusser]

Thanks!
Very helpful and informative.  I will have to try this on some of the tinya nd fragile PE stuff on my armor models.

MR

[Tom Neeson]

By sweat soldering, do you mean heating with a torch? Great technique, thanks.

Tom

[RoughboyModelworks]

Tom:

Sweat soldering is the application of heat to melt solder on tinned pieces that are held in position by some mechanical means. The pieces are heated until the solder melts and flows or "sweats." No additional solder is applied to the joint while heating. The method of applying heat depends on the size of the joint to be soldered and the materials being joined. In many cases a torch can be used, it's usually the fastest, but for very small, delicate pieces or complex assemblies, a soldering iron of appropriate size or a resistance soldering unit would be preferred. Using a torch on small pieces or castings, you risk distorting or in the worst case, melting the casting. For the demonstration, I used a torch as it was the most expedient means of melting the tinned solder.

Paul

[Tom Neeson]

Thanks for the explanation Paul. Will definately be useful when I build another armor model, namely a DML Grille M with all the trimmings from Griffon, lots of brass.

Tom

[finescalerr]

Paul, that was a great technique and the photos clearly show the value of Neolube. I need to find something to solder together to try that. Excellent. -- Russ

[lab-dad]

VERY HELPFUL!
Thanks a million for the class professor!
Guess I need to get some neolube now!
FWIW I just recently bought one of those small butane pencil torches at Home Depo and LOVE IT!
Pinpoint heat instantly!
-Marty

[Ken Hamilton]

Could you mix your own "graphite paste" using powdered graphite & alcohol?
Since I have both of the above and not Neolube, I wonder if that would work.......

[RoughboyModelworks]

Thanks guys, glad you all found it useful.

Ken: I don't know if that would work or not. All you can do is try. I think the problem will be getting the graphite to remain in suspension. NeoLube uses Processed Micro Graphite (according to specs, the graphite particles are predominantly 4 microns in size, with the largest being 10 microns... pretty tiny particles) and a thermoplastic resin as a binder, at least according to their label. It's made by Huron Industries in Port Huron, MI, a government contractor. Here is a link to the specs for NeoLube. P-B-L sells it, but their price is high, $10 for 2 oz. MicroMark sells it, but their price is even worse, $16.95 for 2 oz. I bought a quart on eBay for $16.00 a couple of years ago. I think regular quart price is around $95.00 so I guess the message is, check eBay.

NeoLube is a conductive lubricant. As an aside I love the advertising photo on the Micromark site, showing drivers painted with NeoLube. They say it's "ideal for blackening locomotive wheels." Idiots, you do that, instant short circuit... obviously something they didn't bother to check.

Marty: yes, those butane pencil torches are great, love mine too.

Paul

[davej]

Carr's have something in their range if there is a stockist near you, otherwise I guess they ship to Canada -

Carr's Solder Mask 15ml. This is a graphite-based paste, which prevents solder from getting to unwanted places. It also acts as a barrier to Loctite. It forms a good dry lubricant and conducts electricity. It is useful for the assembly of linkage pins, where the head of the pin has to allow rotation and the shank is soldered solid with the second part.

d

[SandiaPaul]

I'm sorry I did not look it up to make sure, but I am pretty sure PBL sells Neolube.

I will add my belated "thank you" for taking the time to show this technique, very helpful! I had never heard of it before.

Thanks,

Paul

[Hauk]

I'm sorry I did not look it up to make sure, but I am pretty sure PBL sells Neolube.

You are absolutely right.
Lifted from the homepage of PBL:
NEOLUBE Paintable Dry Lubricant 2 oz-UPS ONLY         $ 9.95   
http://www.p-b-l.com/Pbl2002/main-ws-ltm.html

Look here: Online Catalog> Solder>Page 3   

Regards, Håvard H

[Ray Dunakin]

Cool technique! I already have some neolube, for blackening running gear and such. Nice to have another use for it.

[RoughboyModelworks]

Thanks Paul and Ray... I'm always finding more uses for the stuff. A few years ago I rebuilt the movement for a tall-case clock. After some problems getting the escapement to work consistently, I tried NeoLube on the mating parts. It's been running great ever since with no further need for lubrication.

Another tip: it's great for representing surfaces polished through wear. If you use it over a black paint finish, then buff it with a soft sable brush after it dries, it takes on a polished steel sheen - very good for handrails, levers, foot pedals and so so. Used on nickel silver, it looks very much like oily steel, great for running gear in addition to its lubricating properties.

Paul

[Lawton Maner]

I first encountered Neolube (or its father) in 1971 while helping to build the nuclear powered Crusiers California and North Carolina at what was then Newport News Shipbuilding and Drydock Company. 

We used it for an tapping compound arround nuclear pipe (mostly atainless steel) because the alcohol flashed off and left on mess like oil based fluids do.  Also a drop in a padlock and it will never freeze up on you. 

A warning though: because it is a carbon based material with fantastic penetrating power it will make almost anything it touches conduct electricity.  We used it to lubricate the bearings on HO Scale locomotive wheels but made sure there was nothing arround that we didn't want to contaminate.  A drop applied with a toothpick and you never had to do it again.

It was a bit strange that you needed a supervisor's permission to get a 2 gram tube of superglue but could just walk up to the supply shack and get a 2 oz. bottle of Neolube which as I recall cost about $90.00 (because of its nuclear rating) at the time.