Technology Applications Group
810 48th Street South
Grand Forks, ND 58201
(701) 746-1818
(800) TAGNITE


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Whether it is a main transmission housing for a helicopter or a gearbox for a jet engine, most all magnesium castings in the aerospace industry are painted because paint provides excellent protection against magnesium corrosion. Critical to the overall benefit paint provides is its adhesion to the magnesium substrate. The surface of the Tagnite coating is ideal for paint and consistently outperforms other magnesium coatings on paint adhesion related evaluations.

Oftentimes, a paint surface can become damaged due to its contact with a hard sharp object such as a mechanics tool. In these instances, it is important to have an excellent base for the paint to help prevent corrosion migration from the damaged area. Causing even more damage to the magnesium component. The Tagnite coating has the surface porosity needed for excellent paint adhesion and the stand alone corrosion resistance necessary to help keep corrosion from aggressively migrating from damaged surfaces. paintvert2.jpg (20598 bytes)

One of the most effective tests for judging the ability of a paint base to help keep corrosion from aggressively migrating from a damaged surface is to scribe magnesium test panels with a sharp instrument penetrating the paint and coating layer leaving bare magnesium exposed. Once scribed, the panels are placed in salt spray and evaluations are taken on regular intervals to determine how far corrosion has migrated from the scribe line to undamaged areas. This type of evaluation is often done in accordance with ASTM-D1654.

Shown below are photos of ZE41A test plates which have been exposed to salt spray for 14 days (336 hours). The left side of each test plate is a machined surface while the right side of each plate is as-cast. Each plate was scribed prior to exposure to salt spray. After being coated with thin TAGNITE, Dow 17 or HAE, plates were painted with MIL-P-2377 or PR330 primer (1).

 

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a) Light DOW 17+MIL-P-23377 b) Light HAE+MIL-P-23377 c) Light TAG 8200+MIL-P-23377
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d) Light HAE+PR330 e) Light TAG 8200+PR330

Shown below are photos of ZE41A test plates which have been exposed to salt spray for 14 days (336 hours). The left side of each test plate is a machined surface while the right side of each plate is as-cast. Each plate was scribed prior to exposure to salt spray. Some plates have been surface sealed with one or three coats of Rockhard while others were not surface sealed (1). As you can see from photos B and C, plates coated only with Tagnite were able to withstand the harsh salt spray exposure far better than plates coated with only HAE or Dow 17, photos A and F.

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a) Light HAE b) Light TAGNITE 8200 c) Heavy TAGNITE 8200
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d) Light HAE+1 Coat Rockhard e) Light TAGNITE 8200+ f) Light Dow 17
1 Coat Rockhard
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g) Light HAE+3 Coats Rockhard h) Light TAGNITE 8200+ i) Heavy TAGNITE 8200+
3 Coats Rockhard 3 Coats Rockhard

1) *James H. Hawkins, "Assessment of Protective Finishing Systems for Magnesium," Presented at the International Magnesium Association's 50th Annual World Magnesium Conference, Washington, D.C., May 11-13, 1993

*Complete copy available upon request.

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