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The Tagnite Coating

Tagnite, the most corrosion and abrasion resistant anodic coating for magnesium alloys is formed in an electrolytic cell and classified as an anodize coating.  The coating was designed as a replacement for the Dow 17 and HAE anodize coatings which lack the properties needed in today’s demanding aerospace and defense industries.

While at first glance the Tagnite coating system may seem like a typical anodize process, it is in fact a highly advanced and sophisticated process bearing few similarities to Dow 17 and HAE anodize.  Like typical anodize coatings, the part to be coated is connected to a conductive rack which carries the part throughout the coating process.  Once placed in the Tagnite coating tank, the rack and part become the anode and the tank holding the electrolyte serves as the cathode.

The electrolyte used to form the coating is an alkaline solution clear in color, containing no chromium (VI) or other heavy metals and operates below room temperature (40° to 60° F).  This contrasts sharply with the Dow 17 electrolyte, a chromic acid based electrolyte containing a significant amount of chromium (VI), operating between 160° and 180° F and is dark orange in color.  The HAE electrolyte (dark purple in color) contains permanganate, an oxide form of the manganese metal, and is a heavy metal similar to chromium.

The proprietary rectifier used to apply the coating was designed specifically for Tagnite.  It employs a unique waveform optimized for the coating process.  To ensure maximum corrosion resistance and high dielectric strength, the Tagnite coating is applied at voltages exceeding 300 volts DC.  The Dow 17 coating may be applied with AC or DC power and typically does not exceed 100 volts. HAE is applied using AC current and typically does not exceed 125 volts.

Unlike Dow 17 and HAE anodize which primarily builds thickness by surface deposition resulting in large pores and a softer coating, Tagnite is formed by the build up of hard, tightly packed magnesium oxide from the base of the coating.  The coating consists mostly of hard magnesium oxide with minor surface deposition of hard fused silicates.

The Tagnite coating can be applied as thin as 0.10 mil or as thick as 0.9 mil depending upon the alloy being coated.  The white color of the Tagnite coating does not vary with coating thickness, a clear demonstration that the coating is primarily hard white magnesium oxide.

TAGNITE-8200 Type I   TAGNITE-8200 Type II
Color: White   Color: White
Coating Thickness: 0.35 mil Coating Thickness: 0.90 mil
Alloy: ZE41A Alloy: ZE41A Test Plate
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