Atmospheric Corrosion Study of Electrodeposited Hard Chromium and High-Velocity Oxygen-Fuel Thermal Spray Coatings

ABSTRACTElectrodeposited hard chrome (EHC) plating is used commercially to produce hard, wear-resistant coatings on new or refurbished parts. This process requires hexavalent chromium, which has undesirable environmental effects.1 Therefore, a new, environmentally benign process is being developed f...

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Bibliographic Details
Published in:Corrosion (Houston, Tex.) Tex.), 2002-02, Vol.58 (2), p.119-123
Main Authors: Natishan, P.M., Lawrence, S.H., Foster, R.L., Sartwell, B.D.
Format: Article
Language:English
Subjects:
Aluminium
Aluminum
Applied sciences
Atmospheric corrosion
Chromium
Coated electrodes
Coatings
Cobalt
Corrosion
Corrosion prevention
Corrosion tests
Exact sciences and technology
Fuels
Metals. Metallurgy
Oxygen
Production techniques
Sprayed coatings
Steel
Substrates
Surface treatment
Tungsten
Tungsten carbide
Uniform attack (corrosion)
Velocity
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Summary:ABSTRACTElectrodeposited hard chrome (EHC) plating is used commercially to produce hard, wear-resistant coatings on new or refurbished parts. This process requires hexavalent chromium, which has undesirable environmental effects.1 Therefore, a new, environmentally benign process is being developed for giving surfaces a hard, corrosion-resistant coating. A replacement coating for EHC must possess fatigue, wear, corrosion, impact, and mechanical properties equal to or better than those of hard chrome. A promising technique to produce hard, wear-resistant coatings that could replace EHC plating in a number of applications is high-velocity oxygen-fuel (HVOF) thermal-sprayed coating.2-3 In HVOF, an explosive gas mixture ignites in the barrel of a spray gun, which partially melts the powdered coating material and propels it in a carrier gas toward the substrate at supersonic speeds. HVOF uses oxygen and a fuel gas as the combustion propellant. The HVOF process is capable of depositing metal alloy, ceramic/metal composite, and polymer coatings rapidly and to thickness values comparable to those of EHC plating. In this article, results are reported and compared as to how well the EHC and HVOF coatings provide protection against corrosion of Type 4340 (UNS G43400)(1) steel and 7075 aluminum (UNS A97075) substrates during a 3-year atmospheric exposure.EXPERIMENTAL PROCEDURESCommercial samples of Type 4340 steel and 7075 aluminum were used. The substrate dimensions for all but two samples were 4 by 6 by 0.2 in. Two 7075 aluminum substrates that received HVOF
ISSN:0010-9312
1938-159X
DOI:10.5006/1.3277311