Electrodeposited Nanocrystalline Co-P Alloy Coatings as a Hard Chrome Alternative
Abstract
The replacement of hard chrome plating in aircraft manufacturing activities and maintenance depots is a high priority for the U.S. Department of Defense. Chromium plating baths contain chromic acid, in which the chromium is present in the hexavalent state (Cr+6), a known carcinogen having a high level of toxicity. Nanocrystalline cobalt-phosphorus (nCoP) is an environmentally benign alternative to engineering hard chrome plating (EHC). The nCoP coatings are applied to both line-of-sight and non-line-of-sight surfaces using similar electroplating processes. This program aimed to qualify to the technology for use in applications currently specified for EHC. Overall, nCoP met the majority of acceptance criteria as defined in the Joint Test Protocol and showed excellent performance in demonstration and validation field testing. The results showed that nCoP exceeded EHC performance in corrosion and sliding wear tests. The abrasive wear performance of nCoP by Taber wear was poor as previously determined, while gravelometry testing showed equivalent performance relative to hard chrome. Fatigue and hydrogen embrittlement testing showed nCoP met or exceeded performance of EHC. While further testing may be required to support General authorization, it is anticipated that nCoP may be widely specified per MIL-DTL-32502 - Coating, Cobalt-Phosphorus Alloy, Nanocrystalline (Electrodeposited) as a hard chrome alternative on the basis of testing completed to date.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 05, 2017
- Accession Number
- AD1064242
Entities
People
- John Benfer
- Keith Legg
- Neil Mahalanobis
- Ruben A. Prado
Organizations
- Naval Air Systems Command