Aluminium
Why aluminum can be anodized and what is it about? Anodized aluminum is an electrically oxidized aluminum. An oxide layer is electrochemically deposited on the aluminum surface, increasing the resistance of this surface. At the same time, different colors can be obtained by anodizing.
Aluminum windows in a large city have dark stains after a few years, which cannot be removed even by thorough cleaning. Why such stains can appear on the untreated aluminum surface?
Aluminum is susceptible to alkalis and some acids, therefore it is digestible. Etching is formed under the influence of environmental pollutants, where dirt adheres and cannot be removed.
What tests should be carried out on the aluminum substrate before applying the coating? How are substrate defects diagnosed??
Substrate examination and defect identification:
| Subject of the study | Test method | Identifying features of the defect |
| Surface contamination with oil (in fact, it rarely occurs on surfaces) | apply absorbent paper (for approx. 1 min) | paper saturated with oil becomes transparent |
| Metallic aluminum | attempting to scratch with a coin or the edge of a knife | a coin pulled with a slight pressure leaves a scratch mark |
| Aluminum anodized | attempting to scratch with a coin or the edge of a knife | a coin pulled with a slight pressure leaves a scratch mark |
| Chemically treated aluminum surface
a) dyed yellow b) dyed green c) dyed according to a special method |
a scratch test with a coin or a knife edge is visually recognizable | a scratch mark remains
a) yellow b) green color c) dark grey (anthracite) |
| Lacquered aluminum parts Clear lacquer | visual inspection or test to dissolve in solvent | strongly shiny, swellable and dissolves |
| Covering varnish | visual inspection or test to dissolve in solvent | colorful, strongly shiny, swellable and dissolves |