Process and device for forming ceramic coatings on metals and alloys, and coatings produced by this process

A process for forming ceramic coatings on metals and alloys in an electrolytic bath fitted with a first electrode and filled with aqueous alkaline electrolyte, in which is immersed the article, connected to another electrode, wherein a pulsed current is supplied across the electrodes so as to enable the process to be conducted in a plasma-discharge regime, the process comprising the steps of:

• i) supplying the electrodes with high-frequency bipolar pulses of current having a predetermined frequency range;
• and
• ii) generating acoustic vibrations in the electrolyte in a predetermined sonic frequency range so that the frequency range of the acoustic vibrations overlaps with the frequency range of the current pulse, wherein each current pulse has a form comprising an initial steep increase of current to a maximum over a time that is not more than 10% of the total duration of the pulse, followed by an initially rapid and then more gradual decrease in the current to 50% or less of its maximum.

A process for forming ceramic coatings on metals and alloys in an electrolytic bath fitted with a first electrode and filled with aqueous alkaline electrolyte, in which is immersed the article, connected to another electrode, wherein a pulsed current is supplied across the electrodes so as to enable the process to be conducted in a plasma-discharge regime, the process comprising the steps of:

• i) supplying the electrodes with high-frequency bipolar pulses of current having a predetermined frequency range;
• and
• ii) generating acoustic vibrations in the electrolyte in a predetermined sonic frequency range so that the frequency range of the acoustic vibrations overlaps with the frequency range of the current pulses, further comprising the step of introducing ultra-disperse solid particles into the electrolyte and creating a stable hydrosol by way of the acoustic vibrations.

A process for forming ceramic coatings on metals and alloys in an electrolytic bath fitted with a first electrode and filled with aqueous alkaline electrolyte, in which is immersed the article, connected to another electrode, wherein a pulsed current is supplied across the electrodes so as to enable the process to be conducted in a plasma-discharge regime, the process comprising:

• supplying the electrodes with high-frequency bipolar pulses of current having a predetermined frequency range, wherein each current pulse has a form comprising an initial steep increase of current to a maximum over a time that is not more than 10% of the total duration of the pulse, followed by an initially rapid and then more gradual decrease in the current to 50% or less of its maximum.