Birchwood’s Tru Temp black oxide process operates at 200-205°F, enabling short-run part finishing without the hazards of hot black oxide. With no boiling chemicals, the process uses a chemical reaction based solely on sodium-salt compounds and is free of EPA-regulated metals. The process line also can be configured to avoid the use of volatile organic compounds.
The Tru Temp process operates with mild alkaline chemistry in a two-stage oxidation process that neither embrittles metal nor creates salt bloom in and around recessed parts. Other coatings, such as zinc phosphate can cause hydrogen embrittlement and etching of metal surfaces, the company says.
Tru Temp produces a durable, satin, black magnetite coating 0.5-microns-thick, with no effect on material hardness or tensile strength. According to Birchwood, the finish can withstand as many as 100 hours of neutral salt spray (ASTM B 117) or several hundred hours of humidity (ASTM D 1748).