procedures for the application of black amorphous ueberzuegen on ferrous metals

摘要

In a phosphate coating process the metal surface such as a ferrous material is treated with an acid aqueous solution containing a coating phosphate and a benzene derivative containing at least two nitro groups and a sulphonic acid group as an accelerator. The accelerator which is present in a concentration of 0.1-5 g./1. may be dinitrobenzene sulphonic acid and alkyl or chloro substituted derivatives such as: 2,4 dinitrobenzene-1-sulphonic acid, 4,6 dinitrochlorobenzene-2-sulphonic acid, 2,6 dinitrotoluene-4-sulphonic acid. Other accelerators such as nitrates and chlorates may also be present in solution and the coating phosphates specified are those of zinc, manganese, iron and calcium.