Determination and optionally regulation of accelerator concentration in zinc phosphonating solution for steel, zinc (alloy)-plated steel and aluminum (alloy) uses biochemical hydrogen peroxide sensor giving electrical signal

摘要

Determination (M1) and optionally regulation of accelerator concentration in zinc phosphonating solution containing steel, steel plated with zinc (Zn) (alloy) and/or aluminum (alloy) with a solution containing Zn ions, phosphate ions and specified accelerator(s) (I) comprising determining the (I) concentration using a biochemical hydrogen peroxide sensor that gives an electrical signal with a magnitude, is new. Phosphation of metal surfaces, comprising steel, steel plated with zinc (Zn) or Zn alloy, aluminum (Al) and/or Al alloy involves spraying or dipping for 3 seconds to 8 minutes with a solution containing 0.2-3 g/l Zn ions and 3-50 g/l phosphate ions, such that the weight ratio of phosphate ions to Zn ions is = 3.7, and accelerator(s) (I). (I) comprises 0.3-4 g/l chlorate ions, 0.01-0.2 g/l nitrite ions, 0.05-2 g/l m-nitrobenzene sulfonate ions, 0.05-2 g/l m-nitrobenzoate ions, 0.05-2 g/l p-nitrophenol, 0.005-0.15 g/l free or combined hydrogen peroxide, 0.1-10 g/l free or combined hydroxylamine, 0.1-10 g/l reducing sugar, 0.05-4 g/l organic N-oxide, preferably N-methylmorpholine, and/or 0.5-5 g/l organic nitro compound selected from nitroguanidine, nitroarginine, its (m)ethyl and propyl esters and nitrofurfurylidene diacetate. The novelty is that the (I) concentration is determined using a biochemical hydrogen peroxide sensor that gives an electrical signal with a magnitude from which the (I) concentration can be determined.