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Does paint affect EMI of enclosure

Plastic enclosure for small productCustom Enclosure Design?Standard enclosure sizes?Weather protected enclosureLight- and vapor-tight enclosure entryEMI protection for unused pinsWill EMI strongly affect my sensor readingMaking aluminium conductive for an RF shield enclosureCooling an outdoor electronics enclosureUse of internal PCB ground plane as ESD baseplate/EMC reference plane of product in plastic enclosure

4

$begingroup$

This could be a very stupid question but when it comes to RF you never know.

Does painting (non-conductive) over the top of a grounded metal enclosure affect its ability to absorb/block RF interference? At the mechanical fixings the enclosure is not painted and has a good ground connection.

I was wondering because I remembered that RF currents travel on the surface of conductors. Would they just travel "beneath" the paint??

Thanks, Jack.

emc enclosure

share|improve this question

edited 1 hour ago

Jack the Lad

asked 2 hours ago

Jack the LadJack the Lad

263

New contributor

Jack the Lad is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  What kind of paint?
  $endgroup$
  – Eugene Sh.
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Non-conductive paint
  $endgroup$
  – Jack the Lad
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  This is a qualified it depends. If you paint over a ground plane then no. If it's part on an enclosure and the the paint acts as an insulator between the lid and the base, both conductive then yes. This is not a detailed explanation of why but I will leave that for a proper answer.
  $endgroup$
  – Warren Hill
  1 hour ago
  

  
  
  
  

add a comment | 

4

$begingroup$

This could be a very stupid question but when it comes to RF you never know.

Does painting (non-conductive) over the top of a grounded metal enclosure affect its ability to absorb/block RF interference? At the mechanical fixings the enclosure is not painted and has a good ground connection.

I was wondering because I remembered that RF currents travel on the surface of conductors. Would they just travel "beneath" the paint??

Thanks, Jack.

emc enclosure

share|improve this question

edited 1 hour ago

Jack the Lad

asked 2 hours ago

Jack the LadJack the Lad

263

New contributor

Jack the Lad is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  What kind of paint?
  $endgroup$
  – Eugene Sh.
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Non-conductive paint
  $endgroup$
  – Jack the Lad
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  This is a qualified it depends. If you paint over a ground plane then no. If it's part on an enclosure and the the paint acts as an insulator between the lid and the base, both conductive then yes. This is not a detailed explanation of why but I will leave that for a proper answer.
  $endgroup$
  – Warren Hill
  1 hour ago
  

  
  
  
  

add a comment | 

$begingroup$

This could be a very stupid question but when it comes to RF you never know.

Does painting (non-conductive) over the top of a grounded metal enclosure affect its ability to absorb/block RF interference? At the mechanical fixings the enclosure is not painted and has a good ground connection.

I was wondering because I remembered that RF currents travel on the surface of conductors. Would they just travel "beneath" the paint??

Thanks, Jack.

emc enclosure

share|improve this question

edited 1 hour ago

Jack the Lad

asked 2 hours ago

Jack the LadJack the Lad

263

New contributor

Jack the Lad is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

share|improve this question

edited 1 hour ago

Jack the Lad

asked 2 hours ago

Jack the LadJack the Lad

263

New contributor

Jack the Lad is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 1 hour ago

Jack the Lad

asked 2 hours ago

Jack the LadJack the Lad

263

New contributor

Jack the Lad is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 hours ago

Jack the LadJack the Lad

263

New contributor

Jack the Lad is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 2 hours ago

Jack the LadJack the Lad

263

2 Answers
2

active

oldest

votes

5

$begingroup$

Does painting (non-conductive) over the top of a grounded metal
enclosure affect its ability to absorb/block RF interference?

No, the idea of an EMI enclosure is to create a faraday shield around something to block electromagnetic waves around whatever it is enclosing. The shield itself needs to be conductive to be effective and have adequate skin depth, on the inside of the shield the electric field is zero (assuming there are no radiators on the inside). (The skin depth needs to be larger for a faraday shield to be effective, but for most metals anything more than 5mm is effective against 0.1Hz)

For a faraday cage to be effective, it needs to be conductive and continuous as possible (slots and apertures can provide inlets for electric fields to bleed in).

As long as the surface of the enclosure is conductive and continuous, it will have the same blocking power even with materials of different conductivity on the outside. If anything the paint will attenuate high frequencies or change the reflection (because any two materials that have a boundary have reflection and transmission coefficents).

In short, adding paint to the surface of a metal enclosure will not change the conductivity of the metal underneath (unless there is some kind of severe chemical reaction, which is unlikely). And ad the end of the day it is the conductivity of the metal enclosure that matters most.

share|improve this answer

answered 1 hour ago

laptop2dlaptop2d

25.6k123279

$endgroup$

add a comment | 

2

$begingroup$

Well, although laptop2d answer is correct, if you interpret the word "ability" in a somewhat different sense, some kind of paints could actually improve the overall shielding provided by the underlying metal enclosure.

In fact the paint could reduce the incoming RF wave energy, dissipating it as heat. That's the principle behind what are called RAM (Radiation Absorbent Materials), which are used, for example, on stealth vehicles.

Such paints can also be non-conductive. For example, microscopic iron balls are coated in an insulating film and then deployed on the surface to coat embedded in an insulating epoxy matrix. So, overall, the coating is non-conductive.

share|improve this answer

answered 50 mins ago

Lorenzo DonatiLorenzo Donati

16.9k44476

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  They actually make a wide variety of conductive paints that can block RF in various frequencies (especially 2.4ghz) nowadays
  $endgroup$
  – laptop2d
  13 mins ago
  

  
  
  
  

add a comment | 

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5

$begingroup$

Does painting (non-conductive) over the top of a grounded metal
enclosure affect its ability to absorb/block RF interference?

No, the idea of an EMI enclosure is to create a faraday shield around something to block electromagnetic waves around whatever it is enclosing. The shield itself needs to be conductive to be effective and have adequate skin depth, on the inside of the shield the electric field is zero (assuming there are no radiators on the inside). (The skin depth needs to be larger for a faraday shield to be effective, but for most metals anything more than 5mm is effective against 0.1Hz)

For a faraday cage to be effective, it needs to be conductive and continuous as possible (slots and apertures can provide inlets for electric fields to bleed in).

As long as the surface of the enclosure is conductive and continuous, it will have the same blocking power even with materials of different conductivity on the outside. If anything the paint will attenuate high frequencies or change the reflection (because any two materials that have a boundary have reflection and transmission coefficents).

In short, adding paint to the surface of a metal enclosure will not change the conductivity of the metal underneath (unless there is some kind of severe chemical reaction, which is unlikely). And ad the end of the day it is the conductivity of the metal enclosure that matters most.

share|improve this answer

answered 1 hour ago

laptop2dlaptop2d

25.6k123279

$endgroup$

add a comment | 

5

$begingroup$

Does painting (non-conductive) over the top of a grounded metal
enclosure affect its ability to absorb/block RF interference?

No, the idea of an EMI enclosure is to create a faraday shield around something to block electromagnetic waves around whatever it is enclosing. The shield itself needs to be conductive to be effective and have adequate skin depth, on the inside of the shield the electric field is zero (assuming there are no radiators on the inside). (The skin depth needs to be larger for a faraday shield to be effective, but for most metals anything more than 5mm is effective against 0.1Hz)

For a faraday cage to be effective, it needs to be conductive and continuous as possible (slots and apertures can provide inlets for electric fields to bleed in).

As long as the surface of the enclosure is conductive and continuous, it will have the same blocking power even with materials of different conductivity on the outside. If anything the paint will attenuate high frequencies or change the reflection (because any two materials that have a boundary have reflection and transmission coefficents).

In short, adding paint to the surface of a metal enclosure will not change the conductivity of the metal underneath (unless there is some kind of severe chemical reaction, which is unlikely). And ad the end of the day it is the conductivity of the metal enclosure that matters most.

share|improve this answer

answered 1 hour ago

laptop2dlaptop2d

25.6k123279

$endgroup$

add a comment | 

$begingroup$

Does painting (non-conductive) over the top of a grounded metal
enclosure affect its ability to absorb/block RF interference?

No, the idea of an EMI enclosure is to create a faraday shield around something to block electromagnetic waves around whatever it is enclosing. The shield itself needs to be conductive to be effective and have adequate skin depth, on the inside of the shield the electric field is zero (assuming there are no radiators on the inside). (The skin depth needs to be larger for a faraday shield to be effective, but for most metals anything more than 5mm is effective against 0.1Hz)

For a faraday cage to be effective, it needs to be conductive and continuous as possible (slots and apertures can provide inlets for electric fields to bleed in).

As long as the surface of the enclosure is conductive and continuous, it will have the same blocking power even with materials of different conductivity on the outside. If anything the paint will attenuate high frequencies or change the reflection (because any two materials that have a boundary have reflection and transmission coefficents).

In short, adding paint to the surface of a metal enclosure will not change the conductivity of the metal underneath (unless there is some kind of severe chemical reaction, which is unlikely). And ad the end of the day it is the conductivity of the metal enclosure that matters most.

share|improve this answer

answered 1 hour ago

laptop2dlaptop2d

25.6k123279

$endgroup$

share|improve this answer

answered 1 hour ago

laptop2dlaptop2d

25.6k123279

answered 1 hour ago

laptop2dlaptop2d

25.6k123279

answered 1 hour ago

laptop2dlaptop2d

25.6k123279

2

$begingroup$

Well, although laptop2d answer is correct, if you interpret the word "ability" in a somewhat different sense, some kind of paints could actually improve the overall shielding provided by the underlying metal enclosure.

In fact the paint could reduce the incoming RF wave energy, dissipating it as heat. That's the principle behind what are called RAM (Radiation Absorbent Materials), which are used, for example, on stealth vehicles.

Such paints can also be non-conductive. For example, microscopic iron balls are coated in an insulating film and then deployed on the surface to coat embedded in an insulating epoxy matrix. So, overall, the coating is non-conductive.

share|improve this answer

answered 50 mins ago

Lorenzo DonatiLorenzo Donati

16.9k44476

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  They actually make a wide variety of conductive paints that can block RF in various frequencies (especially 2.4ghz) nowadays
  $endgroup$
  – laptop2d
  13 mins ago
  

  
  
  
  

add a comment | 

2

$begingroup$

Well, although laptop2d answer is correct, if you interpret the word "ability" in a somewhat different sense, some kind of paints could actually improve the overall shielding provided by the underlying metal enclosure.

In fact the paint could reduce the incoming RF wave energy, dissipating it as heat. That's the principle behind what are called RAM (Radiation Absorbent Materials), which are used, for example, on stealth vehicles.

Such paints can also be non-conductive. For example, microscopic iron balls are coated in an insulating film and then deployed on the surface to coat embedded in an insulating epoxy matrix. So, overall, the coating is non-conductive.

share|improve this answer

answered 50 mins ago

Lorenzo DonatiLorenzo Donati

16.9k44476

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  They actually make a wide variety of conductive paints that can block RF in various frequencies (especially 2.4ghz) nowadays
  $endgroup$
  – laptop2d
  13 mins ago
  

  
  
  
  

add a comment | 

$begingroup$

Well, although laptop2d answer is correct, if you interpret the word "ability" in a somewhat different sense, some kind of paints could actually improve the overall shielding provided by the underlying metal enclosure.

In fact the paint could reduce the incoming RF wave energy, dissipating it as heat. That's the principle behind what are called RAM (Radiation Absorbent Materials), which are used, for example, on stealth vehicles.

Such paints can also be non-conductive. For example, microscopic iron balls are coated in an insulating film and then deployed on the surface to coat embedded in an insulating epoxy matrix. So, overall, the coating is non-conductive.

share|improve this answer

answered 50 mins ago

Lorenzo DonatiLorenzo Donati

16.9k44476

$endgroup$

share|improve this answer

answered 50 mins ago

Lorenzo DonatiLorenzo Donati

16.9k44476

answered 50 mins ago

Lorenzo DonatiLorenzo Donati

16.9k44476

answered 50 mins ago

Lorenzo DonatiLorenzo Donati

16.9k44476