Reaction of Free-chlorine and Aluminum
Combined free chlorine and hydrogen become hydrochloric acid, but it has high
dissociation and most of it becomes chlorine ions. These chlorine ions react with
the aluminum. The order of the reactions is represented below.
1.) Hydration of oxide film
AlO3 + 3H2O > 2Al(OH)3
2.) Reaction of hydrated oxide film and chlorine (Dissolution of film)
Al(OH)3 + 3HCl > AlCl3 + 3H2O
3.) Reaction of aluminum and hydrochloric acid (Dissolution of aluminum)
Al + 3HCl > AlCl3 + 3/2H2
4.) Precipitation of aluminum hydroxide
AlCl3 + 3H2O > Al(OH)3 + 3HCl
The entire reaction can be summerized as the following:
Al + Al2O3 + 3HCl3 + 3H2O > 2Al(OH)3 + AlCl3 + AlCl3 + H3/2
Therefore the compounds produced by the reactions are aluminum hydroxide and hydrochloric
acid from reaction #4; the hydrochloric acid is not consumed and acts as a catalyst.
Composition Boi ling Point (°C) Common Nam e
1.1.1-Trichloroethane 74.1 Chlorosen
Trichloroethylene 87.2 Trichlene
Tetrachloroethylene 121.1 Perchloroethylene
Solvents that should not be used
Additional Cleaning Notes:
1.) Solvents containing CFC’s destroy the ozone layer and should be avoided to protect the global environme n t .
2.) To avoid solvent residue between the capacitor ’s seal and the PC board, make sure the assembly is dried
thoroughly immediately after cleaning.
Coating
Below is a list of coatings that are safe for use with V-Chips
Ma nufa cturer Ma te ria l Coa ting Ma te ria l Na m e
Acr ylic Ta ffi- 1 1 4 1 , Ta ffi- 1 1 4 7
Urethane Taffi-1154
A cry li c Humi S eal 1B 66
Uret ha ne Humi S ea l 1A 27
Dow Corning S ilicon P erugan Z, P erugan C
Ni hon Zeon Uret hane Q uin at e Syst e m 160B
Hi t achi Chemi cal
Boxy Brown
Application Guide, Aluminum SMT Capacitors