High Temperature Ceramic Coatings

[Brad93]

Anyone have any experience?

I have a fan from a very large industrial oven (gas fired) which keeps corroding and becoming fouled up with dust and corrosion

I need some sort of coating to protect the fan at temperatures of around 300°C which is what it probably experiences in the heat exchanger.

Now in boiler houses we would metal spray with inconel and then ceramic coat with a vitrifying paint which cures when the boiler is fired.

Not suitable for this application because of balancing and the detail of the blades like the nooks and crannies.

Cerakote is the name that keeps coming up but that is more for exhausts isn't it?

 

[Brad93]

Here's the fan

It's 400mm in diameter and 200mm deep

 

[Brad93]

It needs to be balanced and possibly trued before any coating can take place

 

[sako243]

I've not personally tried it but some people I know and trust their judgement on do recommend the ceramic coatings for exhausts.

Funnily enough I've started looking into it for the 6x6 exhaust as it's close to the starter and various other bits. It's supposed to keep external bits of the exhaust really nice and cool by comparison so negates the need for heat shields etc.

 

[oldbikedavey]

Copper plating ?

 

[Munkul]

Make a new one from stainless? It would be easier than you think with laser cutting a slot and tab design.

 

[Ross365]

You could try this outfit https://www.poeton.co.uk/surface-treatments/common-engineering-problems/anti-corrosion/ I know I worked with them once but cannot remember what it was.

When I worked in the nuclear industry, silica coatings were highly thought of, but a quick look on Google failed to identify any UK companies offering such. It would be dipped in a silica rich goo then baked.

 

[Mick Annick]

Anyone have any experience?

I have a fan from a very large industrial oven (gas fired) which keeps corroding and becoming fouled up with dust and corrosion

I need some sort of coating to protect the fan at temperatures of around 300°C which is what it probably experiences in the heat exchanger.

Now in boiler houses we would metal spray with inconel and then ceramic coat with a vitrifying paint which cures when the boiler is fired.

Not suitable for this application because of balancing and the detail of the blades like the nooks and crannies.

Cerakote is the name that keeps coming up but that is more for exhausts isn't it?

I’ve not used them but these people are a spin-off from the nuclear industry and have a good reputation: https://zircotec.com/

 

[Agroshield]

More a question than a statement:

If you find a coating supplier, could the fan be cleaned/blasted adequately to accept that coating?

There is the practical aspect of blasting the gaps between the blades and then the quality aspect of whether the finished item is good enough to accept the coating.

 

[Brad93]

Make a new one from stainless? It would be easier than you think with laser cutting a slot and tab design.

In my experience this would need to be produced from 321 or other type of stabilised stainless to deal with the repeated heating and cooling in the combustion chamber - not to mention the humidity of a bread oven which introduces steam directly into the chamber. This will then render this uneconomical.

 

[Brad93]

More a question than a statement:

If you find a coating supplier, could the fan be cleaned/blasted adequately to accept that coating?

There is the practical aspect of blasting the gaps between the blades and then the quality aspect of whether the finished item is good enough to accept the coating.

Not sure, maybe tumbling would clean between the fins suitably?

 

[Brad93]

I’ve not used them but these people are a spin-off from the nuclear industry and have a good reputation: https://zircotec.com/

I'll send them an email but they look expensive

 

[Haz87]

I'll send them an email but they look expensive

Zircotec coating for (car) exhaust manifolds is commonly £500+
The fan isn't that big, so it might not be overwhelingly expensive.. but the shape and crevices etc may add "additional" labour straight onto that bill

Edit: A quick google suggests prices have actually come down a little (for manifolds). I didn't think anything cost less these days...

 

[Brad93]

I will send them an email. I'll also send a message to @sasquar as this is his area of expertise

 

[chrismac]

I was going to suggest devcon blue or red, text below, would something like that be a worthy experiment?

Brushable Ceramic Blue or Red
Description: A brushable, high performance ceramic-filled epoxy for sealing, protecting and repairing surfaces subject to erosion,
corrosion and wear.
Intended Use: Industrial Use: Protect pump casings, impeller blades, gate valves, water boxes, and fan blades; rebuild heat exchangers,
tube sheets, and other water circulating equipment; top coat on repaired surfaces; seal and protect new equipment
exposed to erosion and corrosion
Features:
Temperature resistance to 350°F (177°C)
Applies easily with short-bristle brush or roller
Low viscosity, self-leveling liquid
Limitations: Suitability of product is determined by the end user for their application and process.
Typical Technical data should be considered representative or typical only and should not be used for specification purposes.
Physical
Properties: Cured 7 Days @ 75°F (24°C) Typical Values Standard Tests
Adhesive Tensile Shear 2,000 psi (13.8 MPa) Adhesive Tensile Shear ASTM D 1002
Brush Coat Thickness 10-20 mils (0.254-0.58 mm) Compressive Strength ASTM D 695
Coefficient of Thermal Expansion (x10-6) 27.5 in/in.°F (49.5 cm/cm.°C) CTE ASTM D 696
Compressive Strength 13,200 psi (91 MPa) Cure Shrinkage ASTM D 2566
Coverage (0.015 in / 0.38mm) 7.6 ft2/lb (1.56 M2/kg) Dielectric Constant ASTM D 150
Cured Hardness 86 D Flexural Strength ASTM D 790
Cured Shrinkage 0.0020 in/in (0.0020 cm/cm) Hardness Shore D ASTM D 2240
Dielectric Constant 3.87 @ 1 MHz
Flexural Strength 8,000 psi (55 MPa)
Salt Spray Resistance 5,000 hrs
Solids by Volume 100%
Specific Volume 16.5 in3/lb (0.596 cm3/g)
Temperature Resistance Wet: 302°F (150°C), Dry 350°F (177°C)

 

[sako243]

I was going to suggest devcon blue or red, text below, would something like that be a worthy experiment?

@Brad93 mentions 300°C which nullifies those coatings temperature resistance ratings. Although maybe Brad means that the core temperature of the heat exchanger is 300°C rather than presumably the outside where the fan sits?

 

[chrismac]

@Brad93 mentions 300°C which nullifies those coatings temperature resistance ratings. Although maybe Brad means that the core temperature of the heat exchanger is 300°C rather than presumably the outside where the fan sits?

ah I was looking at Deg F not Degs C, thanks for spotting that. I wont delete the post ........ makes the replies look pointless if they remain.

 

[Brad93]

@Brad93 mentions 300°C which nullifies those coatings temperature resistance ratings. Although maybe Brad means that the core temperature of the heat exchanger is 300°C rather than presumably the outside where the fan sits?

No this will see 300°C where this sits which rules out any epoxy or belzona/Devcon type products.

It also needs to be a product which won't off-gas and remains inert at high temperatures which basically only allows a thermal sprayed coating by HVOF or Ceramic Coating which is either vitrified to create a bond with the base metal or applied via plasma / chemical deposition.

 

[mtt.tr]

How long do they last?

 

[indykid]

How long do they last?

How much do they cost and how many times the original life do you want them to last?

Stainless squirrel cage fans are apparently available. Is there something off the shelf that would suit your needs?

I only went as far as the first page of google, but maybe ask the question of this lot:
https://www.axair-fans.co.uk/mdi-medium-pressure-stainless-steel-fans

If not, what about nickel electroplating/electroless nickel? Metal plating feels like a more durable and foodsafe approach.