Sn plating solution turns violet: surprising clues

Summary for sn plating solution Discussion

Sn plating solution is turning violet, and Marsella Putri asks what might have happened and whether potassium stannate can react with metals other than copper. In response, the answer notes that the only purple tin-related reactions the writer has heard of are purple of Cassius (gold plus tin) and a tin-ion test using cacotheline, both of which seem unlikely here. The key advice is to identify the type of tin bath being used—acid or alkaline—because unusual color changes are often pH dependent or related to whether the tin is present as Sn+2 or Sn+4. The answer does not identify a definite cause, but suggests that the bath chemistry itself is the most important clue and that a tin plater with direct experience may need to weigh in.