High pH and high tensile stress in nickel sulfamate

A. The obvious answer is to add sulfamic acid to lower the pH ... especially since you're working at bench scale...

I'd also check the boric acid content.

A. Boric acid: test by a lab analysis. I would run a few standards in nickel solution before being positive of what the endpoint looks like. It can be missed easily.
Boric works best at a near saturation level. One way to do the boric is to add it until some settles out with no agitation going. Filter out the excess (at temperature) and keep it for later additions. When the solution cools down, a good bit of the boric will precipitate. No sweat, just agitate well after the temperature is brought back up. Boric does NOT enter into the reaction, so the only source of loss is dragout.

High pH is bad-bad-bad. If you want the proper properties of your nickel, the pH has to be correct, namely 3.9 to 4.1 .

High chloride should not be a problem, unless it is at a ridiculous level. Chloride is routinely added for anode corrosion. Your phrase 4:1 nickel to chloride is open to confusion. Is this as ion to ion or compound to compound?
Yes, a solution that is 4 parts nickel as metal to 1 part chloride is mega too high. Do not dump the solution, but use some of it as a starter solution or for chloride adds.

You really need a book or a copy of the analysis for all of the components of your bath, or you have a good probability of having poor to bad results. IE, you are wasting time and money by trying to do this yourself without doing the proper background work.
Lots of good books are out there and your vendor should be able to provide you with operations and analysis sheets.

Matt, being from over the water and in the UK, I would prefer to talk in terms of g/l for bath make-ups; this is because US gallons are smaller than UK gallons and there is a risk of ambiguity and confusion. Anyway, I reckon your first problem is the high chloride level. The thing about nickel sulphamate is that when it is used with S-nickel rounds, it does not need chloride to promote anode dissolution. I accept that most electroformers add some nickel chloride, but generally not more than 10g/litre as nickel chloride. Chloride is well known for causing stress in deposits, so its must be kept as low as practically possible. Secondly the nickel sulphamate is best used at pH = 3.8-4.2. In a small lab scale tank this may be difficult to control, so you will need great care and good process control. The boric acid level should be between 30 and 40g/l; I have never really encountered any problems with boric acid, unless it is too low and then the pH buffering doesn't work! Your temperature seems OK to me - you can run nickel sulphamate up to 70C, but NO MORE; any higher will give you stress problems because the sulphamate breaks down to sulphate and ammonium ions - the ammonium causes stress. As far as current density is concerned, I would recommend using about 20-30ASF, which is 0.14-0.21A/in^2. You make no mention of any additives in the bath - I like to use about 0.1-0.3g/l of sodium saccharin - it gives a bright deposit with a reasonable hardness and a bright surface. However, you will also need to add other things such as surfactants and these can get quite complicated unless you know the chemistry you are using. Presumably your supplier can tell you what the purchased bath contains.

A. The person that sold you the solution has an obligation to provide you an operations data sheet that lays out all of the parameters that you need to meet and how to adjust things like pH.
Boric acid has 3 H ions in it, so it has three points that it will try to hold a given pH. When you are close to one of the points, but not dead on it or off a bit the other direction, it does not take much to raise the pH.
Add boric to the bath directly until you can see a bit on the bottom and then filter the solution. You now have the correct amount to start with. Boric additions after that should be by analysis.
For the sulfamate tank, I left the anodes in the solution unless I was not going to use it for a month or so. My preference was to store my large anodes in a 35 gal barrel that was full of DI water. For my Woods nickel tank, I would pull those anodes if they were going to be inactive for a couple of weeks.
There is only one person that knows what your anodes are and that is the person that you bought it from. Ask them the direct question and ask for certifications of the material.
I think that you bought stuff from a person with minimal knowledge of his product and one that does not care about customer service.
Sulfamate solution is not a trade secret! How they manufacture it and how they purify it are trade secret information. There are zero additives. You need to buy and add your own anti pit material, normally from the same vendor as a package. If you carbon treat it, you will take out much of the anti-pit that you add. The tank needs to be carbon treated periodically to remove breakdown products and stray stuff out of the air and drag in.
Jim

A. Matt, there is something wrong here - the pH should not increase so much after only 1A-hr. A few things are missing from your submissions; what is the volume of your nickel tank and the size of th electroforms you are trying to make? The amount of additions you are making makes me think the tank is very large, but adding 45g boric acid and 50g of sulphamic acid doesn't add up. To require 50g of sulphamic acid would suggest either the pH is way off or the tank is volume is high, yet to add 45g of boric acid to stabilise the buffering seems strange for the implied size.
I know that my next suggestion may be seen as almost treason to some electrofomers, but I would suggest the boric acid is added to the bulk tank and not into the anode bags. The boric acid works on the bulk electrolyte and cathodic side, not on the anodic side, where you need low pH's to dissolve the metallic nickel. Once the nickel bath is made up, you should never need to add large volumes of boric acid if you keep the tank regularly analysed - either a simple powder addition or a slurry should be adequate.
Finally, when concentrations of nickel sulphamate are quoted, it is as the salt - nickel sulphamate is unstable when dry and is always (or at least should always be!) sold as an aqueous solution. Consequently any waters of hydration are irrelevant.

 Thanks to everyone for your comments and advice. This is an update just to let everyone know how things worked out, especially those who might come across this thread via a search engine.

The bath volume is 2gal, and yes, the pH was initially way high so I had to add a lot of sulfamic acid to bring it down.

I purchased the small nickel sulfamate kit from platingsales.com, and after several attempts on the phone to get more information on the bath, anodes, etc. I gave up. I always spoke to the same person, who kept telling me that the person I *really* needed to talk to wasn't there, but he never returned my calls. The person I did talk to never did believe that I was having residual stress problems (and didn't seem to know what that was), and kept blaming my substrate or my cleaning procedure. Obviously, I would not recommend this supplier again because of their poor customer service and apparent lack of basic knowledge.

Thanks to this forum, I now know to keep a close eye on pH and maintain it near 4 by adding a little sulfamic acid powder(1-2g) from time to time as needed. I've had very good results electroforming up to several hundred microns thick onto gold-sputtered polymer templates, including polycarbonate and photolithography resists.