HCl media resistant coating
01-18-2008, 04:50 AM,
#1
HCl media resistant coating
Hi, Gordon, do you have any coating recommendation for HCl media resistant? Thank you. Jeff.
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01-18-2008, 06:07 AM,
#2
RE: HCl media resistant coating
AC-HVAF Arc spray whith Titanium

jeffsays163 Wrote:Hi, Gordon, do you have any coating recommendation for HCl media resistant? Thank you. Jeff.
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01-19-2008, 05:43 PM,
#3
RE: HCl media resistant coating
Hi Jeff

Some materials which show some resistance to hydrochloric acid solutions (not necessarily in TSC form): alumina and chromium oxide ceramics, Metals and alloys NiCu, CuNi, NiCrFe, NiCrMo, Mo, W, Ta, Ti and not forgetting many plastics, fluorocarbon polymers (not in any order of preference).

Temperature, concentration (or may be we are taking dry HCL gas) and any other chemicals that may be involved will dramatically effect the corrosion potential.

Is the coating only to give corrosion protection or does it also require other properties like wear resistance?

Coatings will require to be 100% effective barrier to the environment. Some coatings will require careful sealing with sealers that are also resistant to the environment.

exnnerspray kind suggestion along with Hastelloy C and Inconel 625 type coatings or may be these coatings used as a base coat for chromium oxide ceramic or a fluorocarbon polymer may be worth consideration. May be just a simple plastic lining will be the answer. You will need to consider all the factors carefully when deciding on a coating system, and then really the coating system needs testing in that environment before you give any lifetime guarantees.
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01-19-2008, 05:45 PM,
#4
RE: HCl media resistant coating
Hi exnnerspray

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exnnerspray Wrote:AC-HVAF Arc spray whith Titanium

jeffsays163 Wrote:Hi, Gordon, do you have any coating recommendation for HCl media resistant? Thank you. Jeff.
Reply
01-24-2008, 01:17 PM,
#5
RE: HCl media resistant coating
Gordon, thank you so much for your full instruction. There are 50% NaCl in the vassel, together with 25% HCl and others for reaction inside, Temp is 60 degree C. The original process of treating the vessel inner wall was Tantalum plating. As you meantioned alumina and chromium oxide ceramics, so APS is the choice?

Thank you exnnerspray also, but as im not familiar with Titanium spraying, may I ask you why AC-HVAF arc is choosed, instead of regular arc spray machine? Will it be OK spray Titanium by Arc, I thought Titanium can be only processed under controlled atmosphere. Anyway, could you give more info? Thanks
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01-27-2008, 07:14 PM,
#6
RE: HCl media resistant coating
Hi Jeff

Quote:As you meantioned alumina and chromium oxide ceramics, so APS is the choice?
Plasma spray will probably be the best choice, although a few HVOF systems can apply high quality ceramics, but at relatively low spray rates and poor deposit efficiencies. Even with ceramic coatings I would be inclined to use something like Hastelloy C or Inconel 625 as a base coat ideally using HVOF/HVAF.

Quote:Thank you exnnerspray also, but as im not familiar with Titanium spraying, may I ask you why AC-HVAF arc is choosed, instead of regular arc spray machine? Will it be OK spray Titanium by Arc, I thought Titanium can be only processed under controlled atmosphere. Anyway, could you give more info?
Yes, ideally titanium needs needs to be sprayed under controlled atmosphere. Titanium oxidises quite aggressively with oxygen present during spraying. Also titanium has a bad habit of absorbing gases like oxygen and nitrogen and becoming very brittle and prone to cracking. To arc spray titanium you really need to use argon atomising gas instead of air or pure nitrogen and may be an additional argon shroud. Not sure about HVAF titanium coatings, but should be better than HVOF for oxidation and gas absorption. Cold spray (cold gas-dynamic spraying process) potentially has a good future with this type of coating. I don't think its quite there yet for today Sad
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01-28-2008, 07:13 AM,
#7
RE: HCl media resistant coating
Thank you Gordon!!
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02-19-2009, 08:00 PM, (This post was last modified: 02-19-2009, 08:48 PM by djewell.)
#8
RE: HCl media resistant coating
As Exnnerspray said, HVAF-ARC sprayed Titanium could be an option because the coating is very dense. The titanium would be sprayed in a reduced oxygen environment, which is a big advantage over regular Arc. Past tests with HVAF-ARC showed no permeability above a minimum thickness.
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