SOS !!! yellow stain on WC coating
03-29-2018, 12:12 PM,
#1
Lightning  SOS !!! yellow stain on WC coating
hello all, i have a big issue on carbide tungsten coating. we met a issue on the roller coating surface, it appears some yellow stain, vendor told me this is due to waters or moisture.
my question is, WC coating suppose to have a corrision resist why this happen? is this related to the porosity seal not good?
how can we fix this issue? if need disassemble the roller will take me 2 wks, this is a pain workSadSad

question 2: we have strick roughness requirement on the coating surface, 225 - 275 μin. what kind of seal is recommended to use, our normal use is phenolic seal, it will make roller shining, customer want a matte looking, any suggestion?

https://drive.google.com/file/d/16tBwvsS...sp=sharing

https://drive.google.com/file/d/1yAT_WaK...sp=sharing
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03-29-2018, 02:14 PM,
#2
RE: SOS !!! yellow stain on WC coating
online waiting!!
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03-29-2018, 03:20 PM,
#3
RE: SOS !!! yellow stain on WC coating
(03-29-2018, 02:14 PM)zhuminkun Wrote: online waiting!!

From pictures it looks like coating peeled off in these areas. Is it just a stain ? If it peeled off i'm afraid there's not much you can do but to recoat.
But that's just me - you should wait for the other replies.
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03-29-2018, 04:46 PM,
#4
RE: SOS !!! yellow stain on WC coating
Hi zhuminkun

Sign0016 to the Surface Engineering forum.

What type of WC coating?
What process type used to produce coating?
Was coating sealed?
Coating thickness?

It appears that the coating is not impervious to the environment and has allowed corrosion of the substrate underneath coating causing coating damage and the rust staining.
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03-29-2018, 11:45 PM,
#5
RE: SOS !!! yellow stain on WC coating
(03-29-2018, 04:46 PM)Gordon Wrote: Hi zhuminkun

Sign0016 to the Surface Engineering forum.

What type of WC coating?
zhu:HVFO
What process type used to produce coating?
Was coating sealed?
zhu: need to check with vendor
Coating thickness?
zhu: 0.12mm.

It appears that the coating is not impervious to the environment and has allowed corrosion of the substrate underneath coating causing coating damage and the rust staining.

i assume the seal may not good, got lots of porosity not sealed.
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04-01-2018, 11:09 AM,
#6
RE: SOS !!! yellow stain on WC coating

I agreee with Gordon, seems that the coatings was not gas tight, or liquid tight, and corrosion has come through the surface.

Has this happened before? Did you coat in house?



(03-29-2018, 04:46 PM)Gordon Wrote: Hi zhuminkun

Sign0016 to the Surface Engineering forum.

What type of WC coating?
What process type used to produce coating?
Was coating sealed?
Coating thickness?

It appears that the coating is not impervious to the environment and has allowed corrosion of the substrate underneath coating causing coating damage and the rust staining.

Stephen James Booth
www.ipsteknokraft.com
www.teknokraft.com
Indonesia WhatsApp +6281905603262

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04-02-2018, 01:18 PM,
#7
RE: SOS !!! yellow stain on WC coating
(04-01-2018, 11:09 AM)Stephen Booth Wrote: I agreee with Gordon, seems that the coatings was not gas tight, or liquid tight, and corrosion has come through the surface.

Has this happened before? Did you coat in house?



(03-29-2018, 04:46 PM)Gordon Wrote: Hi zhuminkun

Sign0016 to the Surface Engineering forum.

What type of WC coating?
What process type used to produce coating?
Was coating sealed?
Coating thickness?

It appears that the coating is not impervious to the environment and has allowed corrosion of the substrate underneath coating causing coating damage and the rust staining.

it is coated in-house for sure, i suspect the seal is not spray properly, that's only reason i doubt. the trick thing is we require the seal is transprant seal, means we need to keep the orginal color of the carbide tungsten. do you have any recommendation about the seal can meet this spec.?
Reply
04-05-2018, 04:52 PM,
#8
RE: SOS !!! yellow stain on WC coating
(03-29-2018, 12:12 PM)zhuminkun Wrote: hello all, i have a big issue on carbide tungsten coating. we met a issue on the roller coating surface, it appears some yellow stain, vendor told me this is due to waters or moisture.
my question is, WC coating suppose to have a corrision resist why this happen? is this related to the porosity seal not good?
how can we fix this issue? if need disassemble the roller will take me 2 wks, this is a pain workSadSad

question 2: we have strick roughness requirement on the coating surface, 225 - 275 μin. what kind of seal is recommended to use, our normal use is phenolic seal, it will make roller shining, customer want a matte looking, any suggestion?

https://drive.google.com/file/d/16tBwvsS...sp=sharing

https://drive.google.com/file/d/1yAT_WaK...sp=sharing
Consider other material, maybe a nickel based alloy/super alloy applied through HVOF. Sealing could work but i`m not related with the seal application, so i can`t help with that, sorry.
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