removal or stripping of coatings
07-20-2007, 04:02 PM,
#1
removal or stripping of coatings
I am new to the surface engineering forum. I work for a company which uses a unique technology for cleaning which includes stripping of oxides and coatings. We don't use any acids or other environmentally hazardous materials (so we don't attack the substarte) and it creates a unique surface profile suitable for good adhesion of coatings. This technology can be also used for coating (yes something which removes coatings can be also used to deposit coatings, unique isn't it?) and surface modification of metal surfaces.
I am trying to find out how big is the market for stripping of coatings, especially in the aerospace and tool manufacturing section. Do aerospace companies/ jet engine manufacturesrs require a lot of stripping of the coatings and how about companies making tool steel?
If any one can proivide me with some statistics about the market for stripping and removal/polishing of surfaces, it will help us in deciding to introduce this technology into the market.
Thank you,
George
Reply
07-24-2007, 03:45 PM,
#2
RE: removal or stripping of coatings
Hi George (Mountprat)

Sign0016 to the Surface Engineering Forum.

There is always need of easier alternative methods of stripping coatings. Sorry, can't really help with market statistics, though I would be interested in more details of your process.
Reply
07-27-2007, 02:34 PM,
#3
RE: removal or stripping of coatings
We have a hybrid process which is a patented technology of our company. This is a very fast process and environmentally friendly.
Reply
07-30-2007, 06:26 PM,
#4
RE: removal or stripping of coatings
mountprat Wrote:We have a hybrid process which is a patented technology of our company. This is a very fast process and environmentally friendly.
Reply
07-30-2007, 06:28 PM,
#5
RE: removal or stripping of coatings
George Wrote:
mountprat Wrote:We have a hybrid process which is a patented technology of our company. This is a very fast process and environmentally friendly.

Sorry about the empty prior reply...i am learning.

Mountprat:

Could you let us know what the hybrid process consists of?


Thanks,
George
Reply
07-31-2007, 05:08 PM,
#6
RE: removal or stripping of coatings
Hi George

Sign0016 to the Surface Engineering Forum.

Our choice at the moment:
  • Machining/grinding
  • Hammer and chisel
  • Grit/shot blasting
  • High pressure water blasting
  • Dry ice blasting
  • Chemical/electrochemical stripping
  • Thermal shock
  • Mixture of above
Any other methods I've missed?
Reply
12-05-2008, 06:58 PM,
#7
RE: removal or stripping of coatings
I am currently seeking a chemical strip method for removing Tunsten Carbide and Chrome carbide from Titanium and A286 substrates. These coating are applied with an HVOF system known, (Jet Kote III), the customer will not allow any sort of mechanical strip methods and must meet all GE aircraft/aerospace requirements. Any suggestions?

Kurt
Reply
12-06-2008, 05:18 PM,
#8
RE: removal or stripping of coatings
Hi Kurt

Sign0016 to the Surface Engineering Forum.

There are some chemical and electrolytic methods, but often require some degree of light mechanical stripping in addition for complete coating removal. The chemical stripping process weakens/degrades the coating and does not necessarily dissolve/remove coating completely, but it can make mechanical stripping very much easier.

I am not familiar with GE aircraft/aerospace requirements for stripping coatings, so really I can only suggest contacting GE directly. We have a few forum members associated with GE work, so hopefully they can comment further.

Quote:the customer will not allow any sort of mechanical strip methods
This sounds a little extreme and I think requires some clarification.
Reply
12-07-2008, 07:04 PM,
#9
RE: removal or stripping of coatings
Hello Gordon,

Thankx for the quick reply, When I stated that the customer would not allow any sort of mechanical stripping, Our CA is somewhat of a particular individual. The waterjet option is out just because of the complex nature of the part, by the time we got it tooled and the waterjet operation done, the cost of stripping would far outweigh what we are being paid to coat the parts, becase it is on an airfoil which must maintain an RA of less than 55, that pretty much eliminates any grit blasting options. We are not set up for any sort of machining or grinding operations, but this may be avenue in which we may have to pursue if I cannot find a recipe that will allow chemical stripping. If the chemical stripping were to attack the coating structure and say remove the cobalt from the coating, we may be able to use gritblasting to lightly remove the remainder of the coating. I have never heard of "Thermal Shock" or "Dry Ice Blasting", would either one of the methods be aggressive enough to remove the coating without being detrimental to relitively soft substrate of A286, (BHN <350 vs Chrome Carbide BHN 1200+)? I have been speaking with some of my friends in the industry and while they have not actually tried it, they have heard that hydorfloric or cyanuric acid,(which I have never heard of) could possibly remove the chrome carbide, I haven't been able to find anyone who has suggestions for the tungsten carbide. We are currently set up for Nitric and Hydrocloric acids on our strip line but have never used agitaion or raised temperatures, I have also heard this may be helpful, but how much should the acid be heated. Our Nitric is a 50/50 mix, and our Hydro/Nitric is 25/25/50. should these recipes be altered and in what way? I am still pursuing my engineering degree, and have not not had an extensive backgroung in chemistry so any comments would be appreiciated. By the way the parts we are attempting to strip are turbine vanes with a dovetail shaped pressure face. There is an erosion coating made up of the Chrome or Tungsten carbide on the airfoil from the platform, through the fillet, and up the airfoil about 0.450". Thankx, Kurt
Reply
12-10-2008, 04:46 PM,
#10
RE: removal or stripping of coatings
o the Surface Engineering Forum.

Our choice at the moment:

* Machining/grinding
* Hammer and chisel
* Grit/shot blasting
* High pressure water blasting
* Dry ice blasting
* Chemical/electrochemical stripping
* Thermal shock
* Mixture of above

Any other methods I've missed?

.......................................
Edit - link removed
Reply
12-10-2008, 07:09 PM,
#11
RE: removal or stripping of coatings
en00g

(12-10-2008, 04:46 PM)en00g Wrote: o the Surface Engineering Forum.

Our choice at the moment:

* Machining/grinding
* Hammer and chisel
* Grit/shot blasting
* High pressure water blasting
* Dry ice blasting
* Chemical/electrochemical stripping
* Thermal shock
* Mixture of above

Any other methods I've missed?
.......................................
Edit - Link removed

Much like your post, your blog seems to consist of copied and regurgitated items from the internet Sad Animal0028 with no original content - shame. Far too much of this already Tazsmili, it makes finding original content difficult.

Sorry, I consider this Sign0014 even though your link was associated with engineering. I have edited out your blog link and deleted a similar post on another thread. Make some sensible and original posts in the forums and I may reconsider allowing your blog link.
Reply
12-16-2008, 06:08 PM,
#12
RE: removal or stripping of coatings
Hi Kurt (kurtecard)

Sorry, if the two posts between this and your last post in this thread were confusing. These are certainly not aim at you personally, just en00g and any other would be spammer Happy0193

Hello Gordon,

Quote:Thankx for the quick reply, When I stated that the customer would not allow any sort of mechanical stripping, Our CA is somewhat of a particular individual. The waterjet option is out just because of the complex nature of the part, by the time we got it tooled and the waterjet operation done, the cost of stripping would far outweigh what we are being paid to coat the parts, becase it is on an airfoil which must maintain an RA of less than 55, that pretty much eliminates any grit blasting options. We are not set up for any sort of machining or grinding operations, but this may be avenue in which we may have to pursue if I cannot find a recipe that will allow chemical stripping. If the chemical stripping were to attack the coating structure and say remove the cobalt from the coating, we may be able to use gritblasting to lightly remove the remainder of the coating. I have never heard of "Thermal Shock" or "Dry Ice Blasting", would either one of the methods be aggressive enough to remove the coating without being detrimental to relitively soft substrate of A286, (BHN <350 vs Chrome Carbide BHN 1200+)? I have been speaking with some of my friends in the industry and while they have not actually tried it, they have heard that hydorfloric or cyanuric acid,(which I have never heard of) could possibly remove the chrome carbide, I haven't been able to find anyone who has suggestions for the tungsten carbide. We are currently set up for Nitric and Hydrocloric acids on our strip line but have never used agitaion or raised temperatures, I have also heard this may be helpful, but how much should the acid be heated. Our Nitric is a 50/50 mix, and our Hydro/Nitric is 25/25/50. should these recipes be altered and in what way? I am still pursuing my engineering degree, and have not not had an extensive backgroung in chemistry so any comments would be appreiciated. By the way the parts we are attempting to strip are turbine vanes with a dovetail shaped pressure face. There is an erosion coating made up of the Chrome or Tungsten carbide on the airfoil from the platform, through the fillet, and up the airfoil about 0.450". Thankx, Kurt
"Thermal shock" rapid heating and cooling, I doubt this would work or be applicable in your case. "Dry ice blasting" I doubt you would consider for same reasons as high pressure water jet blasting.

Hydrofluoric acid I would avoid on health and safety grounds and I'm not sure but may also attack titanium alloy substrate.

Cyanuric acid I've not come across as a stripping chemical. Without actually trying it, I can't say if it would be any use, I doubt it. https://en.wikipedia.org/wiki/Cyanuric_acid

Agitation or raising temperatures and or concentrations of stripping chemicals will generally give a more aggressive action (also possibly towards substrate material). Your nitric acid and acid mix may have some effect on tungsten carbide/cobalt type coatings, but I doubt whether they would be effective on chromium carbide/nickel chromium coatings.

I can only suggest trying electrolytic methods. This process is claimed to work for both tungsten carbide and chromium carbide based coatings on titanium alloy substrates:

Bath make up:
20% sodium carbonate
5% tartaric acid
75% water
(Ashamed0002 not sure whether %weight or %volume)
Temperature 70 - 80 C

Stainless steel cathode, coated parts requiring stripping are made the anode.
Current density 4 - 8 amperes per square inch (0.006 - 0.013 amps/square mm) at 6 volts d.c.

Claimed removal rate for tungsten carbide/cobalt coatings 0.001" (0.025 mm) per 10 minutes.

Hope that helps.
Reply
12-17-2008, 02:45 PM,
#13
RE: removal or stripping of coatings
(07-20-2007, 04:02 PM)mountprat Wrote: I am new to the surface engineering forum. I work for a company which uses a unique technology for cleaning which includes stripping of oxides and coatings. We don't use any acids or other environmentally hazardous materials (so we don't attack the substarte) and it creates a unique surface profile suitable for good adhesion of coatings. This technology can be also used for coating (yes something which removes coatings can be also used to deposit coatings, unique isn't it?) and surface modification of metal surfaces.
I am trying to find out how big is the market for stripping of coatings, especially in the aerospace and tool manufacturing section. Do aerospace companies/ jet engine manufacturesrs require a lot of stripping of the coatings and how about companies making tool steel?
If any one can proivide me with some statistics about the market for stripping and removal/polishing of surfaces, it will help us in deciding to introduce this technology into the market.
Thank you,
George

Mountprat,

I work in the aircraft overhaul and maintenance industry, mainly on aircraft landing gear systems, which utilise large quantities of chrome, nickel and cadmium plated coatings. In my experience chrome plating is stripped on a regular basis, I would say that on average we strip 5 components every day. These can range from small pins to large 6 foot long cylinders. Cadmium on the other hand is stripped and replaced at every overhaul interval. I would be interested to learn more about your stripping method and if it can be used to remove electroplated coatings as well as thermal spray and PVD coatings.
Reply
12-17-2008, 05:22 PM,
#14
RE: removal or stripping of coatings
Hi mepgssp

Sign0016 to the Surface Engineering Forum.
Reply
12-18-2008, 09:21 PM,
#15
RE: removal or stripping of coatings
(12-05-2008, 06:58 PM)kurtecard Wrote: I am currently seeking a chemical strip method for removing Tunsten Carbide and Chrome carbide from Titanium and A286 substrates. These coating are applied with an HVOF system known, (Jet Kote III), the customer will not allow any sort of mechanical strip methods and must meet all GE aircraft/aerospace requirements. Any suggestions?

Kurt

Hi Kurt,
Are you working on a repair of service run parts or rework of failed OEM material? If repair is it a standard book repair or are you developing from scratch, say DER? I ask because a book repair will give you a method to strip (it has to be valid and approved).
Forgive me if I'm wrong but it sounds like you are completing a third party coating renewal process? Do you have access to the full manual and SPM?
Be careful heating up the nitric, it can give off some nasty fumes when heated, although it does strip quicker! Room temp is fine for most applications as long as the concentration is checked.

Jim
Reply
12-20-2008, 06:50 PM,
#16
RE: removal or stripping of coatings
To all and Kurt,

Agree with Jim (turbine repair), I believe refering to the OEM manual for such and stripping process will be the easiest way out. Normally when a repair is developed, esp coating, the design group will also figure out the post repair as this part after engine run will defnitely come back for repair. For a typical repair on thermal spray, removal of old coating surface, prep and re-ccoat will be claerly spelled out in the engine manual, or whichever stripping process will be clearly define in SPM as well.

Unless you are working with the design group to develope such a new technology or ways of stripping a coating.
Reply
06-24-2016, 06:54 AM,
#17
RE: removal or stripping of coatings
(07-20-2007, 04:02 PM)mountprat Wrote: I am new to the surface engineering forum. I work for a company which uses a unique technology for cleaning which includes stripping of oxides and coatings. We don't use any acids or other environmentally hazardous materials (so we don't attack the substarte) and it creates a unique surface profile suitable for good adhesion of coatings. This technology can be also used for coating (yes something which removes coatings can be also used to deposit coatings, unique isn't it?) and surface modification of metal surfaces.
I am trying to find out how big is the market for stripping of coatings, especially in the aerospace and tool manufacturing section. Do aerospace companies/ jet engine manufacturesrs require a lot of stripping of the coatings and how about companies making tool steel?
If any one can proivide me with some statistics about the market for stripping and removal/polishing of surfaces, it will help us in deciding to introduce this technology into the market.
Thank you,
George

Reply
04-22-2019, 02:34 PM,
#18
RE: removal or stripping of coatings
(12-16-2008, 06:08 PM)Gordon Wrote: Hi Kurt (kurtecard)

Sorry, if the two posts between this and your last post in this thread were confusing. These are certainly not aim at you personally, just en00g and any other would be spammer Happy0193

Hello Gordon,

Quote:Thankx for the quick reply, When I stated that the customer would not allow any sort of mechanical stripping, Our CA is somewhat of a particular individual. The waterjet option is out just because of the complex nature of the part, by the time we got it tooled and the waterjet operation done, the cost of stripping would far outweigh what we are being paid to coat the parts, becase it is on an airfoil which must maintain an RA of less than 55, that pretty much eliminates any grit blasting options. We are not set up for any sort of machining or grinding operations, but this may be avenue in which we may have to pursue if I cannot find a recipe that will allow chemical stripping. If the chemical stripping were to attack the coating structure and say remove the cobalt from the coating, we may be able to use gritblasting to lightly remove the remainder of the coating. I have never heard of "Thermal Shock" or "Dry Ice Blasting", would either one of the methods be aggressive enough to remove the coating without being detrimental to relitively soft substrate of A286, (BHN <350 vs Chrome Carbide BHN 1200+)? I have been speaking with some of my friends in the industry and while they have not actually tried it, they have heard that hydorfloric or cyanuric acid,(which I have never heard of) could possibly remove the chrome carbide, I haven't been able to find anyone who has suggestions for the tungsten carbide. We are currently set up for Nitric and Hydrocloric acids on our strip line but have never used agitaion or raised temperatures, I have also heard this may be helpful, but how much should the acid be heated. Our Nitric is a 50/50 mix, and our Hydro/Nitric is 25/25/50. should these recipes be altered and in what way? I am still pursuing my engineering degree, and have not not had an extensive backgroung in chemistry so any comments would be appreiciated. By the way the parts we are attempting to strip are turbine vanes with a dovetail shaped pressure face. There is an erosion coating made up of the Chrome or Tungsten carbide on the airfoil from the platform, through the fillet, and up the airfoil about 0.450". Thankx, Kurt
"Thermal shock" rapid heating and cooling, I doubt this would work or be applicable in your case. "Dry ice blasting" I doubt you would consider for same reasons as high pressure water jet blasting.

Hydrofluoric acid I would avoid on health and safety grounds and I'm not sure but may also attack titanium alloy substrate.

Cyanuric acid I've not come across as a stripping chemical. Without actually trying it, I can't say if it would be any use, I doubt it. https://en.wikipedia.org/wiki/Cyanuric_acid

Agitation or raising temperatures and or concentrations of stripping chemicals will generally give a more aggressive action (also possibly towards substrate material). Your nitric acid and acid mix may have some effect on tungsten carbide/cobalt type coatings, but I doubt whether they would be effective on chromium carbide/nickel chromium coatings.

I can only suggest trying electrolytic methods. This process is claimed to work for both tungsten carbide and chromium carbide based coatings on titanium alloy substrates:

Bath make up:
20% sodium carbonate
5% tartaric acid
75% water
(Ashamed0002 not sure whether %weight or %volume)
Temperature 70 - 80 C

Stainless steel cathode, coated parts requiring stripping are made the anode.
Current density 4 - 8 amperes per square inch (0.006 - 0.013 amps/square mm) at 6 volts d.c.

Claimed removal rate for tungsten carbide/cobalt coatings 0.001" (0.025 mm) per 10 minutes.

Hope that helps.

Hi
Which type of power source are you using?
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