Desmut and Alodine System
Aluminum Desmut – A light smut consisting of various salts or residues of alloy metals such as copper, iron, or manganese can be expected after alkaline etching. An acid treatment is used to remove it and activate the surface.
Alodine, also referred to as iridite, is a chromate conversion coating that is applied only to the surface of aluminum. It gives good corrosion protection as well as providing an excellent base for painting. The case study below is a system developed for a major aerospace manufacturer to process aerospace grade aluminum and aluminum alloy parts with multi-color Alodine 1200 or clear color Alodine 1500. It involves six stages constructed from standard MK Series Immersion Washing Systems.
Each processing chamber has its own transport elevator to automatically take the work into and out of solution. Leaning over open tank(s) and manually placing baskets in and out of solution is eliminated.
The elevator moves the parts into solution and oscillates with either a short or long stroke. A two position switched is used to select either long 5 to 9 inch or short 2 to 4 inch strokes. The long stroke is used to provide better flushing (hydraulically forcing solution though the working area) of nested masses or complex part shapes with recessed passages and/or blind holes whereas the short stroke is used to provide quicker oscillations of simpler parts. Flexibility in stroke ranges and speeds allows for more comprehensive processing of a wider range of parts.
The Process
Stage One – Deoxidizer -Desmut
Stage Two – DI Rinse
Stage Three – DI Rinse
Stage Four – Alodine 1200S
Stage Five – DI Rinse
Stage Six – Alodine 1500
Each stage includes automatic cycle timers with indicating stack lights, front mounted operator controls and roller conveyor platforms for easy lateral transfer between stages without having to lift baskets. Stainless steelpneumatically actuated powered cover are also incorporated into each stage. The cover is interlocked with the pneumatic and electric controls, sequenced to open before the elevator rises and to close only when the elevator has descended. Each stage is thereby operated with the cover normally closed. The covers are only opened for loading/unloading and are otherwise closed. This feature minimizes vapor/air interface thereby reducing environmental concerns. Each tank included seismic hold-downs accessible from the front and rear to comply with local regulations.
Other Desmut and Alodine System can be constructed from the MK Series and MKT Console Series. The process is very similar to the description above. Please note that there are many variations to the Alodine Process. See http://www.henkelaero.com/ for Aerospace Applications.
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