Development of composition and study of properties of a new high-efficiency silicon-containing protective conversion coating on zinc-plated surfaces

The composition was developed for a new high-efficiency silicon-containing protective conversion coating for application to zinc-plated surfaces. It was proven experimentally and theoretically that this new environmentally safe coating is comparable in corrosion resistance and protective power to environmentally hazardous chromate coatings; however, unlike the latter, the former is efficient at high temperatures (to 150°C). For extra protection of a material being coated, it was proposed to additionally apply a new, nontoxic (hazard class 4) organic film based on gallic acid esters.     

Formation and Properties of Nickel–Phosphorus–Graphite Composite Coatings in Autocatalytic Deposition

It is shown that nickel–phosphorus–graphite composite coatings can be deposited by the autocatalytic deposition method. The optimal concentration of graphite and the duration of ultrasonic treatment of a graphite suspension in solution for deposition of composite coatings based on the nickel–phosphorus alloy were determined. The influence exerted by thermal treatment parameters on the properties of the deposits was examined. The optimal process conditions are suggested.     

Microdistributions of Electrolytic Alloys and Their Components

Microdistributions of Cu–Ni and Cu–Co alloys electrodeposited from pyrophosphate; Ni–Cu, from sulfate–chloride and pyrophosphate–ammonium; Cu–Zn, from pyrophosphate and cyanide; Cu–Cd, from sulfate and pyrophosphate; and Ni–Cd, Ni–Co–Cd, and Zn–Cd, from sulfate, sulfate–chloride, pyrophosphate, chloride–ammonium, and acetate electrolytes are studied. The coatings' microprofile depends on the kinetics of reduction of each component and mutual influence of electrochemical processes at the cathode. Copper accelerates and cadmium inhibits the reduction of the second component of alloys, no matter the electrolyte type, reduction kinetics, and metal nature. In antileveling conditions, the diffusion-controlled Cu reduction accelerates the reduction of the second component of alloys and ensures deposition of coatings whose microprofiles are more uniform than expected from diffusion limitations only. Depolarizing action of Cu during the Cu–Zn deposition from a cyanide electrolyte can completely neutralize differences in the rates of supply of reduced metal ions; hence a constant chemical composition of the coating over its microprofile. Inhibiting action of the diffusion-controlled Cd deposition provides for leveling properties of electrolytes from which Ni–Cd, Ni–Co–Cd, and Zn–Cd alloys are deposited; the chemical composition of these deposits is nonuniform over their microprofiles.     

Preparation of gold nanoparticles of desired size and a study of their impact on the photosensitized generation of singlet oxygen in the aquatic phase

The effect of gold nanoparticles on the photooxidation of tryptophan in the presence of porphyrins immobilized on chitosan in the aquatic medium is studied. This reaction is used as a model to assess the sensitizing ability of porphyrins in the photogeneration of singlet oxygen, a process underlying photodynamic therapy, a promising method for treatment of cancer. Gold nanoparticles are prepared by reduction of gold cations with sodium borohydride in the presence of polyvinylpyrrolidone. The proposed technique enables to obtain gold nanoparticles with a very narrow size distribution.     

Silicon-containing Solution for Passivation of Zinc Coatings

Russian Journal of Applied Chemistry - A process was developed for chromate-free passivation of zinc-plated surfaces via formation of conversion silicon-containing coatings on these surfaces. The...     

Passivation of zinc coatings in cerium-containing solutions

Process was developed for no-chromate passivation of zinc coatings in a solution containing 20-40 g L^-1 of cerium nitrate, 5-25 mL L^-1 H₂O₂, and 2-8 g L^-1 of an additive (8-10 g L^-1 of malic acid and 4-8 g L^-1 of sodium nitrate) at a temperature of 40-60°C and pH 2.5-3.5. It was shown that cerium-containing passivating coatings on zinc-plated steel articles compare well in corrosion resistance and protecting capacity with iridescent chromate coatings. It was found that cerium-containing coatings are capable of self-healing and sustain a thermal shock without degradation of their characteristics.