HVOF Corrosion

HVOF Corrosion

March 12, 1991

This test was performed by an independent laboratory. The sample coatings were applied to bars of 4140 steel as follows:

  • Nitrided to approximately .007 – .010-inch depth
  • Chrome plated, .002 – .003-inch thick
  • Plasma spray, tungsten carbide/cobalt powder
  • JK 558 TRIBALOY®™ T-800
  • JK 591, NISTELLE®™ C
  • JK 112, tungsten carbide/cobalt powder

The lower third of the surfaces were immersed in acid concentrates at elevated temperatures. Corrosion was measured by weight loss. The acids and conditions were as follows:

Acid Immersion Time (hours) % Solution Temp.
Hydrochloric (HCl) .5 18.5% 150°F
Sulfuric (H2S04) 6.0 48.0% 146°F
Hydrofluoric (HF) .5 25.0% 140°F
Formic (HCO2H) 1.0 44.0% 150°F

 

The results were as follows:

Corrosion Rate (inches/year)
MATERIAL HCl H2S04 HF HCO2H
1. Nitrided 47.68 .14 3.26 12.39
2. Chrome plated 67.50 2.84 15.34 39.27
3. Plasma spray-tungsten carbide .49 .04 .98 .49
4. JK 558 Tribaloy T-800 10.36 .14 5.18 3.45
5. JK 591 Nistelle C 1.97 .16 .00 2.47
6. JK 112 tungsten carbide .00 .00 1.41 .23