Titanium-Cadmium Plating Q&As, Problems & Solutions

A. I was surprised to realize that it has been 15 years since I have run Ti-Cad, but it is very hard to forget the effort that went into controlling titanium content. In my old 2004 version of BAC 5804, the control limits of Ti is 55-97 ppm in solution ---OR--- 0.1 to 0.7 % in plate. Your 75 ppm is nearly optimum. Your plate % is a bit on the low side but it is okay. I personally would not be concerned that Ti is too low.

I will share what I used to do for Ti concentration...
If you need to get Ti ppm higher, then it is just a matter of getting the peroxide and Ti-paste right. I preferred to add Ti paste additions manually by pre-dissolving about 300 grams in a gallon or so of peroxide (carefully!) then just pouring it into the tank on a batch basis. On the tank, a very slow peroxide on a continuous feed is best. I used small-bore variable speed peristaltic pump for that and would adjust the feed rate as needed to keep the titanium soluble. For me, I found that 400 mL per 24-hr day per every 1000 liters of cad solution was about perfect, but it would depend somewhat on your bath temperature. Controlling it this way is far better at maintaining the concentration of titanium compared to the method that has you slurry-coat Ti-paste onto filters.

? Could you be referring to chemical vapor deposition of titanium carbide or some other of the new coatings being touted as a replacement for Cd plating?

Best regards,

A. Hi Blair

Titanium - Cadmium plating was developed by Boeing as an alternative to many other coatings that supposedly offer no hydrogen embrittlement. For the real inside info call Dave Kelly at ASCO products in Seattle; he has a bath and often installs baths and trains operators; and as far as I am aware he is the ONLY approved source of the Titanium additive .

regards

A. Thread #3575 mentions TiCd plating and another specification number.

A. I believe the primary benefit of Cad-Ti over Cad is lower susceptibility to hydrogen embrittlement. Apparently Titanium affects the grain size of the plate and thus the ability for hydrogen to escape in post plating baking operations. I am not aware of any data to support this, although I believe people in the Boeing Materials Group did a lot of the pioneering work in the 1960's. We have performed Cad and TiCad plating in this facility for about 10 years.

Q. I am curious what process you are changing to and the data you have to support those changes. The aircraft industry has historically been reluctant to remove cadmium plate, but we would entertain moving away from it also.

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A. The following are Boeing approved sub-tier suppliers who perform Ti/Cad for aerospace applications.

• USA California CROWN CHROME PLATING INC
• USA California DRILUBE COMPANY
• USA California EMBEE INCORPORATED
• USA Kansas AIR CAPITOL PLATING INCORPORATED
• USA Michigan DIAMOND CHROME PLATING INCORPORATED
• USA North Carolina CURTISS WRIGHT FLIGHT SYSTEMS
• USA New York LAWRENCE RIPAK COMPANY
• USA Ohio BFGOODRICH
• USA Ohio NUCLEAR PLATING INC
• USA Oklahoma SOUTHWEST UNITED INDUSTRIES INC
• USA Texas MENASCO AEROSPACE TEXAS
• USA Washington ASKO PROCESSING
• USA Washington HYTEK FINISHES COMPANY

A. Neither standard bath is highly efficient, so both introduce the problem. Baking is the usual relief process, but some people who know more material science than I do say that the cadmium or zinc plating entraps the hydrogen so it can't easily get out.

Perhaps your best bet is a low embrittlement cadmium plating process, one which has pores to allow the hydrogen to escape. One I'm familiar with is Boeing's TiCad process; a small amount of titanium is co-deposited and entrained as a powder into the bath and, when plated, it makes the coating porous.

A. Both of the above replies are correct in many respects. First it should be noted that the preplate cycle can cause hydrogen adsorption both from acid pickling and if cleaning is done with the work anodic (not preferred). Secondly, chloride zinc plating, because it has a much higher efficiency, tends to have less embrittlement from hydrogen; however, frequently the deposit itself is brittle!

(regarding defective Ti-Cad plating causing hydrogen embrittlement)

A. Search the site for TiCad plating, Brad. This is a cadmium plating bath that has a tiny dispersion of titanium particles in it which causes the cadmium deposit to be porous and more permeable for the escape of the hydrogen.

A. There is no substitute for a good set of reference books if you are going to do engineering, especially aeronautical.
You will find that there will be some reductions in the original preplated parts when they are plated. A post plate bake is mandatory for either material. This bake is below the tempering temperature of the rod, so you will lose no more than 1Rc.
If the plating is done very well, I seriously doubt that you could measure the difference unless you have a great lab.
If you do not want to bake, use mechanical plating. No hydrogen embrittlement (unless you acid etch).

A. Both of those electroplatings (and their pretreatment steps of cathodic cleaning and acid pickling, if applicable) will cause hydrogen embrittlement. Proper baking for hydrogen embrittlement relief immediately after plating is essential.

There is a low embrittlement cad plating that co-deposits a titanium oxide slurry to provide paths for hydrogen escape. It's sometimes called Ti-cad. Sorry I don't think it complies with the AMSQQP416 you are using.

A. Hi Rob. I don't see why filtering a straight cadmium plating bath should reduce hydrogen embrittlement. On the chance that you have a Ti-Cad bath, though, we appended your inquiry to a thread on that subject. (In Ti-Cad plating, a slurry of small titanium particles is used in the cadmium plating bath. My understanding is that they are occluded into the deposit in a similar fashion to the way diamond particles are occluded into the nickel plating of tools; they offer an improved "ventilation" so that hydrogen can escape better. If you were to filter out the titanium particles, presumably you could cause a hydrogen embrittlement issue).

Please try to describe the situation as fully as you can to 'filter' out the ifs, ands, & buts as much as possible :-)

Regards,

A. Hi Rob,

Just going to ask for a couple of clarifications: the test pieces went through de-embrittlement (also called embrittlement relief) at the same time and temperature as the other test pieces? 1 off failed the load test at 100 hours and a further 1 failed at the higher load?

So places to look, as I don't think filtration of the cadmium plating tank is the problem (but don't discount it completely).
1. Are the test pieces flaw free? I had a problem a number of years ago where the test pieces suddenly started to fail and it turned out a new person was machining them, but was machining in a flaw, causing premature failure.
2. Check your de-embrittlement time and temperature and also the delay between plating and getting the test pieces in the oven. Again, mystery failure of a one off bath load a few years ago turned out that the operator missed the maximum delay time to get the parts in the oven and the embrittlement damage was already done, part failure was very rapid I must admit (less than 24 hours).
3. Check all of the pre-treatments. An electrolytic cleaner can actually cause test failures. Look at immersion times, chemistry, voltage (for electro-cleaners) etc.
4.Check your cadmium plating tank chemistry, plating rate, times and temperatures.

That should get you started in trying to identify the source of the failure.

A. I assume that you are doing work on Boeing parts per BAC5804. Their specification has the test methods for measuring titanium in solution and also titanium in plate. The methods are a bit complicated, but they both require a spectrophotometer to measure the end result at 420nm.