Have you performed a waterbreak test?
You can clean a part till you turn blue, but if it is not clean enough to pass waterbreak, the plate will not hold.
Are you buffing first? Buffing grease is very sneaky and difficult to remove. My recommendation is to use ultrasonics and heat if at all possible. Don't be shy about doubling up on the concentration of SP degreaser and see if that helps. But SP sometimes has some trouble removing buffing grease.
It's not the best, but I've used a cup per gallon of Dawn dishwashing liquid in a heated ultrasonic to pre-strip the buffing grease, then a professional plating cleaner to do a final clean. I get about a 90% success rate afterwards with the waterbreak. If I don't achieve it, I soak it again for another 5 minutes or so in plating cleaner using ultrasonics.
I use a plating cleaner containing lye, heated to about 150-160F. The concentration of lye is about 2oz per gallon along with other soaps and surfactants (the formula is proprietary to the plating supply company, so I have no idea what else is in it). Lye is nasty stuff and it is hazardous to the skin and eyes, but acetone is no bargain either.
Some other folks here have reported success with brake cleaner. I have never tried it. Personally I avoid volatile organic solvents (eg acetone, gasoline, lacquer thinner, etc.) because of flammability and breathing hazards. Further, they really can't do the job as effectively as other things because they essentially thin the grease and it just ends up back on the part in diluted streaks. The lye-based stuff breaks down the grease and makes it difficult for it to cling back to the part, like soap would.
George's point is correct about removing the item from the solution. I've never had any problems with brief current interruptions. But NEVER take the part out of the bath until you are ready to remove it for good.
NOTE: I want to again reiterate that Lye is a very dangerous material. It can cause serious and permanent damage to the eyes and skin. It is nasty stuff and should NEVER be taken lightly. Any time I come near the stuff I wear gloves and goggles.
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