BLACKENING CHEMICAL FOR METAL WORKING
Common Blackening Processes and Chemicals for Metal Working:
1. Hot Blackening:
. Chemicals: Typically involves using an alkaline aqueous solution at high temperatures.
. Process: The metal is dipped in a hot bath of sodium hydroxide, nitrates, and nitrites, which react with the metal surface to form a black oxide layer (magnetite, Fe3O4).
. Applications: Common for ferrous metals like steel and iron.
. Example Products: Birchwood Casey Presto Black® Hot Blackening, Precision Brand Products Black Oxide Kits.
2. Cold Blackening:
. Chemicals: Utilizes a room-temperature chemical bath, often containing selenous acid, copper compounds, and other proprietary agents.
. Process: The metal is cleaned, then immersed in the solution, where it reacts to form a thin, dark coating.
. Applications: Preferred for small parts, low-volume applications, or when a hot process isn't feasible.
. Example Products: Birchwood Casey Presto Black® Gel, Caswell Inc. Cold Blackening Kits.
