Patina

-

Chinese coin from the first century covered with patina A patinated copper roof of the City Hall building in Minneapolis

Patina, patina, verdigris noble - a product of atmospheric corrosion of copper and its alloys in moist air. The surface layer of the patina forms a color coating from light green to gray-green. Its main component (when formed in an uncontaminated atmosphere) is hydroxyl (II) - [Cu (OH)] 2CO3 carbonate. Patina is a durable coating as the last stage of the passivation process. The whole process of covering the metal surface with patina coating lasts several dozen years, although the first symptoms may begin to appear after a few months.

Artificial patination can also be done with chemical methods, for example for ornamental purposes it can be done by immersing objects in ammonium sulphate solution for 12 hours. and then drying them in the open air. On large, exposed surfaces, patina is a desirable phenomenon, treated as a durable decorative coating - for example on roofs covered with copper sheet, and on bronze or bronze monuments (see eg Statue of Liberty).

A patina formed in an atmosphere containing sulfur dioxide also contains hydroxychide (II) - [Cu (OH)] 2SO4, and its coating is not then a protection against further corrosion.

wiki

Comments

Post a Comment

Popular posts from this blog

Pupo Román

-
José René "Pupo" Román Fernández (died 1961) - Dominican general. Curriculum vitae In the Dominican history, when the dictatorial president Rafael Leónidas Trujillo was in power, Roman was his niece's husband and "third person in the state" (Trujillo and SIM Arturo Espaillata). He was the Minister of Armed Forces, a close associate of Trujillo, which did not prevent him from accepting Trujillo's murder in 1961 from the American consul in the Dominican Republic, Henry Dearborn. He led to the murder of Rafael Trujillo on May 30, 1961, but he could not use this to overthrow his followers. He failed to arrest them along with Trujillo's sons such as Ramfis. Ultimately, the conspiracy ended with the conspirators' defeat when Zacarias - chauffeur Trujillo - survived the presidential bombardment and handed over the drafts of the bombers and Arturo Espaillat informed Roman about the death of the commander - at the sight of Arturo Espaillata Roman revealed ...
Read more

Myrmex Indikos

-
Myrmex Indikos, pol. Indian ant - an alleged species of gigantic ants (according to Herodot's description, larger than foxes, but smaller than dogs). The earliest mention of these creatures is dated to the fifth century BC, and its author is Herodotus. According to her, these ants inhabited the deserts of Persia and India and extracted gold from their sands. Several such creatures were kept in the residence of the King of Persia. Gold was to be obtained by caravans made up of several camels in the heat of the day, when the ants were protected underground. You had to do it quickly, because the ants sensed the smell of people and went on the pursuit, and they were deadly dangerous. This story is confirmed by the next accounts: Nearchos, one of the army officers of Alexander Macedoński, and Megastenes - a historian and traveler. The fragment of the Megasthenes (IV-III century BC) preserved in fragments can be seen in the underground mines at the foot of the mountains on the easte...
Read more

Names of streets and squares

-
The names of the streets and squares were originally of a topographical nature, that is, they informed about: Researchers propose two names for these toponyms - urban or plateonimy. S. Urbańczyk points out that the older names were spontaneously formed and sprouted in the daily lives of the inhabitants of the place. The information contained herein was related to the characteristics of the place (eg appearance), important road directions (geographic orientation) or values, functions and economic meanings called places / objects in the settlement for the inhabitants' lives. Former names are protected by law, but are often not respected by managers of the municipality, county or province. Currently the names of streets and squares are given by the commune authorities, county governors or voivodships. There is a tendency to use commemorative names, ie to commemorate deserving people and important events (eg Zygmunt August Street, 3. Maja Street). The names of the districts are ...
Read more