How to solve the problem of difficult to form an oxide film in and around the holes of machined aluminum parts?

There are two main reasons for the formation of oxide films in the holes of machined aluminum parts` profiles and around them:

(1) The machined aluminum parts are washed thoroughly after caustic washing. Alkali which enters the pores during caustic washing fails to be washed cleanly. After the oxidation treatment, the caustic soda flows out of the cylinder, causing the oxide film around the pores to be corroded.

(2) There are liveliness around the hole of the machined aluminum parts. Aluminum tapping screw hole is very astringent, the operator often lacquer to lubricate, if the lack of emulsifier alkali in the alkaline wash, it is difficult to dilute.

Solution:

(1) Wash the machined aluminum parts with gasoline before caustic washing, emulsifier should be added in caustic solution;

(2) The machined aluminum parts should be washed after caustic washing.