Your Anode Did Not Die. Your Power Supply Did.

Most titanium anode complaints start the same way: “coating failed”, “voltage jumped”, “life shorter than quoted”. When we ask for the rectifier datasheet, sometimes the answer is “just a standard 0–40 V supply”. That sentence explains more failures than any coating batch.

MMO titanium anodes are dimensionally stable, but they are not indifferent to what sits upstream. The coating cares about current density, reversal events, dry start, and how dirty the DC really is.

Ripple is not a detail. A switched-mode supply with 20–30% ripple does not just “still make chlorine”. The instantaneous current swings push the anode through repeated micro-cycles of over-current and relaxation. Over months, the Ru-Ir or Ir-Ta layer ages unevenly: edge attack first, then pinholes, then base titanium oxidizes underneath the coating. A buyer sees “anode dead at 14 months” and blames the coating. The rectifier was the co-author.

Polarity reversal is worse than people think. DSA anodes are designed to evolve chlorine or oxygen, not to act as a cathode. If a control fault reverses polarity for even a few seconds, chlorine-side coatings can gas differently, coating adhesion shifts, and titanium substrate may see conditions it was never meant to survive. Some plants survive one event. Many do not.

Dry start is the quiet killer. Someone opens the isolating valve later than the current setpoint. Plates are in air, current flows, titanium base heats, coating cracks before the first litre of brine arrives. No coating survives “electricity before electrolyte”. MMO tolerates short air exposure during maintenance—not a controlled energizing sequence with no liquid.

Acid wash, then power on—wrong order. Operator finishes HCl circulation, closes acid line, forgets rinse, hits start. Residual acid film plus high current density etches the active layer from the edges. The anode did not “wear out naturally”. The sequence wore it out.

What we tell project engineers now: treat the power supply as part of the anode system, not a separate line item. Confirm ripple, confirm interlock between flow switch and rectifier, confirm polarity protection, confirm startup sequence in the PLC, not just on paper. A 5-year coating commitment assumes a 5-year-clean power environment. Change the power side, and the coating life number moves with it.

Buyers spec the anode to the gram of precious metal. Then they hang it on a rectifier nobody reviewed. In the field, the anode is only as good as the current you push through it.