Chrome Oxide Coating: Free Chrome
10-14-2009, 05:59 AM,
#1
Chrome Oxide Coating: Free Chrome
Dear Gordon,
We have sprayed Chrome oxide using plasma spray system. In metallographic inspection a shiny phase is observed. Well these shiny bright phases are observed in many of the chrome oxide coating micro graphs generated by other people .

Can you please let me know how these shiny bright phase can be minimized and from where do they come. We are using 99.95% pure Chrome oxide of H C Starck.

Regards
Girish
Reply
10-14-2009, 11:52 AM,
#2
RE: Chrome Oxide Coating: Free Chrome
Good morning Girish,

I would suggest checking with HC Starck as to whether the Chrome Oxide that they are supplying you with is their acid-washed material or from their re-oxidising manufacturing process.
Simon Hiiemae
Sulzer Metco (UK) Ltd
01633 488 091
emailaddressisSimon.Hiiemae@Sulzer.com
Reply
10-15-2009, 02:30 AM,
#3
RE: Chrome Oxide Coating: Free Chrome
Hi Girish

The metallic phases seen in chromium oxide coatings comes mainly from two sources - free chromium metal in the chromium oxide powder and copper/tungsten from plasma gun hardware. The other possible source is from entrained dust from a booth that has seen spraying of other metallic coatings and has not been cleaned sufficiently or from powder feeders which have not been clean out properly from previous use.

For most applications very small amounts of metallic inclusions will not have any detrimental effect. Laser engraved anilox rolls on the other hand can be very sensitive to this issue.

Many years ago I did some work (from the plasma spraying side) on free chromium (copper/tungsten/other metallic contamination is another matter) that was tuning up in our coatings. I came to the conclusion that little could be done with spraying parameters to improve matters very much, even injecting oxygen into the plasma only had a minor effect. Free chromium appeared to be tightly wrapped up in the chromium oxide powder particles, even acid washing of the powder only led to a minor reduction. Now I think you can get powders that are pretty much completely free of metallic contamination, though you may need to pay a little extra.

If your application really needs extremely low free metal content chromium oxide coatings, then request a high purity low free metal powder. H.C. Stark I'm sure will be very aware of this problem Wink
Reply




Possibly Related Threads…
Thread Author Replies Views Last Post
  Hardness increase in Chrome Ceramic Plasma Coating DMan 6 2,967 03-25-2021, 01:24 PM
Last Post: DMan
  Chrome Oxide Hardness Neufeld 1 2,913 02-18-2020, 09:25 PM
Last Post: Lemster68
  Chrome-Carbide coating issue DanyGans 11 10,369 10-08-2019, 05:19 PM
Last Post: Lemster68
  oxide cluster in NiCrAl plasma coating Zhiguo 5 7,800 09-26-2018, 04:48 PM
Last Post: bpls670
  HVAF tungsten carbide to replace hard chrome - Help??!!! Adamreis 2 4,112 02-20-2017, 11:04 PM
Last Post: Vig
  Ceramic Densification of Chrome Stephen Booth 5 13,601 10-19-2015, 12:59 PM
Last Post: sorousheti
  replacing hard chrome coating on piston grisen 3 5,302 10-08-2015, 12:07 PM
Last Post: Guner
  Hard Chrome failure on Ducati rocker arms!! Ago37 2 6,310 09-06-2014, 09:33 AM
Last Post: Stephen Booth
  Laminar oxide in hvof coating Lazha 2 4,797 02-24-2014, 09:41 PM
Last Post: KevinS
  Chrome Oxide Plasma SG-100 with N2 warx 0 4,033 10-30-2013, 05:54 PM
Last Post: warx
  Applications of Chrome Plating ritesh 5 6,117 05-29-2013, 09:17 AM
Last Post: Laurent
Information Chrome oxide thermal sprayed coatings shelf life Leanne 1 4,389 02-14-2013, 02:18 PM
Last Post: Gordon
Exclamation Cleaning Ceramic (Chrome oxide) coatings - as-sprayed Leanne 1 4,642 02-04-2013, 08:18 PM
Last Post: kschewe
  Oxide stringers in Metco 58NS coating thezombiesprayer 2 6,283 08-13-2012, 09:56 AM
Last Post: thezombiesprayer
  chrome oxide coating failure - 24" dia. steel roll rconnor 3 7,268 07-10-2012, 02:37 PM
Last Post: loriolo



Users browsing this thread: 1 Guest(s)





Surface Engineering Forum Sponsor - Alphatek Hyperformance Coatings Ltd