New possibilities of the porphyrin application. Galvanic covers

Abstract

Influence of introducing small amounts of macroheterocyclic compounds, such as porphyrins, their coordination compounds and phthalocyanines to the electrolytes of galvanic nickel plating and sedimentation of Ni-Co and Ni-Fe alloys to galvanic cover properties has been studied for the first time. 5,10,15,20-Tetra(pyridyl-4’)porphine (H2P1) having basic substituents at the macrocycle periphery, deuteroporphyrin-IX (H2P2) with acidic carboxylic groups, 5,10,15,20-tetrakis(N-methylpyridyl-4’)porphine tetratosylate (H2P3) and tetra-4-sulfophthalocyanine (H2P4) with positively and negatively charged groups of neutral character have been used as tetrapyrrolic compounds. Influence of additives of nickel and cobalt complexes NiP1, NiP3, CoP4, NiP4 and cobalt complex of 4,4’-disulfophthalocyanine (CoP5) on galvanic covers properties has been studied as well. According to atomic-force microscopy data extremely small additions of porphyrins and metalloporphyrins (0.5-5 mg/L) and phthalocyanines (5-50 mg/L) reduce in 2-2.5 times the crystallites size on the cover surface and increase the uniformity of their placement. Thus the level of a roughness decreases in 2-3 times. Microhardness of the covers increases by 20%, microporosity decreases in 6-10 times. Changing of the morphology of the cover surface is obviously caused by high adsorption activity of the macroheterocyclic compounds which block the growing nickel and alloys crystals. This is resulted in growth of cathode polarization by 100-300 mV in the dependence of the additive’s nature. Under the influence of additives of H2P1, H2P2 and H2P3 the polarization curves of sedimentation of nickel and it allows go with high inclination that promotes increasing the electrolytes disseminating ability on average twice. H2P1, H2P2 and H2P3 are the gloss forming additives. Their introduction to the electrolytes composition provides increase of the covers reflective ability up to 80%. The gloss forming effect appears at porphyrin concentration 0.5 mg/L (10-7-10-6 mol/L). It is important that with increase of the cover thickness from 3 to 10 μm the gloss level does not change practically. H2P4 in essentially higher concentrations (5-50 mg/L) shows only small gloss forming effect. It is obviously conditioned by its negative charge which does not promote the tetraanion adsorption on the cathode surface. Blocking the coordination centers of porphyrins and phthalocyanines liquidates the gloss forming effect. The internal tension of the nickel cover when going from the standard electrolyte to that modified with H3P3 decreases from 3390 to 1470 MPa; for Ni-Co allow – from 5310 to 110, Ni-Fe allow – from 4260 to 1100.