Sulfonate electroplating bath, process for refining metal by electrolytic depositing and process for controlling metal morphology in electrolytic refining

An electroplating bath, comprising

• (A) an alkane sulfonic acid or alkanol sulfonic acid;
• (B) a soluble metal salt of alkane sulfonic acid or alkanol sulfonic acid;
• and
• (C) at least one
• polyether derivative of formula (I),
• wherein
• Ar is phenyl substituted by C3-C12-alkyl, or
• naphthyl which is non-substituted or substituted by C1-C4-alkyl,
• E1 and E2 are different from each other and selected from ethyleneoxy and propyleneoxy,
• m is 0 or a number in the range of 1 to 40,
• n is a number in the range of 1 to 40, and
• at least one sulfonated or sulfated polyether derivative of formula (II),
• wherein
• Ar′ is phenyl substituted by C3-C12-alkyl and optionally substituted by a group of —SO3M, or
• naphthyl which is non-substituted or substituted by C1-C4-alkyl and/or a group of —SO3M,
• E1′ and E2′ are different alkyleneoxy groups and selected from ethyleneoxy and propyleneoxy,
• E3 is the alkylene moiety of E2,
• m′ is 0 or a number in the range of 1 to 40,
• o is 0 or 1,
• the sum of n′+o is a number in the range of 1 to 40, and
• M is an alkali metal cation or NH4+.