Section of the Ti wire: the resistance of the lukewarm full length is nearly 1Ω/m. 30A (how much do you have?) would dissipate 900W/m where the wire conducts the full current. That's not huge for a fully immersed wire. Difficult to compute, but you might be near the bubbling limit. Try the same current through you wire in clear water, observe. However, if bubbles stopped the current flowing, you'd notice it at the ammeter.
If you use a current like 30A in a 0.1m long Ti wire (what are your figures?), the voltage drop of 1V (for a current that decreases linearly with the position on the wire) is too big and may create parasitic electrochemical reactions.
The current density in the solution is big near the wire. Plating tries to avoid that. What is the voltage drop in you setup?
Depletion of the solution: let's imagine that you put 30A for 20mn. That would deposit 3g of Cr. You have maybe 100g in the solution. But close to the Ti wire, or within the full-section tube (dimensions?), the solution will be depleted if not stirred. However, you'd notice even a thin layer of chromium, much brighter than zirconium.
Maybe zirconium gets corroded or oxidized in warm acid solution, before any significant layer of chromium deposits on it?
Did you find literature confirming that zirconium can be chrome-plated that way? Does it need a nickel layer first? How does the voltage vary over time at your setup, admitting that the current is constant?
My suggestion is to experiment with variants.
- Connect the wire at both ends if not already done.
- Put several Ti wires in parallel, hold separated from an other by twisted Ti wire.
- Try to deposit Cr on Cu or Ni.
- Replace the Ti wire by Cu (your solution will be polluted after that).
Please be careful
with the chromium compounds. They are seriously dangeroushttps://en.wikipedia.org/wiki/Chromium_trioxide#Safety
and my gut feeling is that you have a limited knowledge margin over this particular setup.
Your titanium wire may also catch fire brutally if it conducts the current and emerges in the air. Small amount, but burning titanium ignites surrounding materials very effectively. Eliminate anything flammable to 1m distance at least.