Black Oxide and Zinc Phosphate Coatings

March 01, 2015

Metal finishers now can achieve both a high quality black oxide finish and a zinc phosphate finish using the same processing system. Safe, simple and inexpensive to operate, this innovative process line from Birchwood Technologies operates with Near-Zero water consumption.

Capable of two unique finishes, it produces a high quality black oxide finish using the proven TRU TEMP low temperature process. In addition, it produces a fine-grained zinc phosphate coating using the MICROLOK MZN process. Both finishes meet many industry requirements and finishing specifications.

Consisting of 10 tanks with 100-gallon capacity, the Dual Process line incorporates a Near-Zero water recycler and an Ion Exchange water purifier. Both processes use common tanks and consume minimal rinse water. Both the blackening and the zinc phosphate process can operate singly or can operate simultaneously.

The answer depends on the customer's finish requirements. In the oil and gas drilling industry, for example, there is a need for both processes to finish different down hole drilling components. Similarly, job shop manufacturers with a variety of machined component projects require the specific advantages found only in each of the processes.

The TRU TEMP process operates at much lower temperatures than conventional processes, providing a high quality finish with long-term corrosion resistance without a dimensional change. It is a direct replacement for hot oxide and complies with Mil Spec MIL-DTL-13924, Class 1 and AMS 2485.

The MICROLOK MZN process is a zinc phosphate fine-grained gray finish. It provides long-term corrosion resistance along with anti-galling and break-in lubricity qualities. It complies with MIL-DTL-16232, Type Z, Class 1, 2 and 3.

The Dual Process line offers the flexibility to operate either process by itself, or both processes simultaneously, as needed. Just one operator can handle all operations with time to spare. One operator can load and unload the system's racks/baskets, process the loads through the line, perform general daily maintenance on the line and produce about 3-4 loads of finished parts per hour. The line can be operated on a full-time or part-time basis, depending on work-flow patterns and part demand.

Related Glossary Terms

  • black oxide

    black oxide

    Black finish on a metal produced by immersing it in hot oxidizing salts or salt solutions.

  • corrosion resistance

    corrosion resistance

    Ability of an alloy or material to withstand rust and corrosion. These are properties fostered by nickel and chromium in alloys such as stainless steel.

  • lubricity


    Measure of the relative efficiency with which a cutting fluid or lubricant reduces friction between surfaces.