Mild corrosion on a circuit board

[phatboy]

Hi all,

Due to a minor leak (Now resolved), there is a bit of mild corrosion on a circuit board in my mechanical heat recovery unit.

I've read about how to clean it with deionised water, but as it is minor, is it even worth doing? If the source of the water has now gone, will it continue to corrode and lead to issues, or remain as is?

Thanks!

 

[JohnW2]

Due to a minor leak (Now resolved), there is a bit of mild corrosion on a circuit board in my mechanical heat recovery unit. I've read about how to clean it with deionised water, but as it is minor, is it even worth doing? If the source of the water has now gone, will it continue to corrode and lead to issues, or remain as is?

Opinions will probably vary. Whilst it is quite probable that, if it now remains dry, no further deterioration will occur, for reasons you suggest it's possible that some potentially corrosive residues (from the leaked water) may still be present, and may eventually do some harm, so it might be wise to give it a little 'wash'.

Kind Regards, John

 

[oldbutnotdead]

Alcohol used to be the weapon of choice for cleaning circuit boards...

 

[Adam_151]

Alcohol used to be the weapon of choice for cleaning circuit boards...

Have you seen the Price of IPA recently?!

 

[oldbutnotdead]

Well yes but its not so bad if you get it through Jeff's tat bazaar

 

[JohnW2]

Have you seen the Price of IPA recently?!

Is not IPA for wimps? - don't the serious drinkers drink meths or surgical spirit, either of which is very cheap (and very toxic!) but ideal for cleaning PCBs

Kind Regards, John

 

[oldbutnotdead]

Is not IPA for wimps? - don't the serious drinkers drink meths or surgical spirit, either of which is very cheap (and very toxic!) but ideal for cleaning PCBs

Kind Regards, John

Meths & surgical spirits both leave residues behind, as well as smelling lovely (not tried drinking them)...preferred burning surgical spirit in my old Mamod steam engine

 

[JohnW2]

Meths & surgical spirits both leave residues behind ...

they do to some extent, but I very much doubt that they are the sort of residues which would ever do any harm to a PCB ... but goodness knows what IPA would leave behind

... as well as smelling lovely (not tried drinking them)...preferred burning surgical spirit in my old Mamod steam engine

I quite like the smell of meths, but not so much the other one - but I certainly would not advise drinking either of them!

Kind Regards, John

 

[mattylad]

Unfortunately John, even though it has dried it still needs cleaning off, microscopic dendrites can still form and cause issues - @phatboy - what was it that leaked onto it??
If you do use IPA then keep it away from anything made of plastic and that may be some of the components/connectors (although they should be able to withstand a little cleaning).
If no IPA then use deionized water as you suggest - but ensure it is left to dry thoroughly before powering up - using a hairdryer can assist with this.

 

[EddieM]

I wouldn't advise using Indian pale ale for cleaning it'll leave a sticky residue.

 

[bernardgreen]

The amount of damage to the PCB will depend on whether the unit was powered at the time the PCB got wet and whether there were any chemicals dissolved in the water.

If there are any safety critical functions then ensure the PCB performs these correctly, otherwise a new PCB should be fitted

If it was not powered then a good clean and effective frying should return it to normal functionality. Some PCB material will absorb water and this can require several days of gentle warmth to fully dry the PCB. Avoid excessive heat as some components will be damaged by heat.

Putting the damp PCB into a bag with a desiccant such as dry silica gel while gently warming can be effective, from time to time drying the silica gel in a hot oven.

If the board was powered when wet then

microscopic dendrites

creating connections between bits that should not be connected together are a definite possibility. They can be very difficult to find and remove.

Even if the board "cleans up" visually there is always the possibility of components having being damaged by current flowing through the water and affecting the internals of the integrated circuits and similar components.

one litre of Isopropyl Alcohol for £16 ( inc VAT ) from RS

 

[davelx]

£13/litre from CPC, but you only need a small spray can for circuit board cleaning with a toothbrush. I keep a can of this on the shelf though:

https://cpc.farnell.com/chemtronics/es1010e/electro-wash-2-5mm/dp/SA01691?st=electrowash

 

[boringoldcodger]

Just living down to my moniker:

If it was not powered then a good clean and effective frying

I'm absolutely certain Bernard meant "drying" ( d & f next to each other on keyboard).

 

[EddieM]

Get 5 litres for £18.94 on fleabay.

https://www.ebay.co.uk/itm/254576346239

 

[phatboy]

Thanks all for the replies,

It's a low voltage board, it's the control board for a Heat Recovery Ventilation unit - https://www.vent-axia.com/range/sentinel-kinetic-bh

It was powered on at the time.... I noticed as the fans were spinning up and down unusually, and the wired remote was showing garbled errors. I initially power cycled it, and all went back to normal, but it had reset to factory... even the hours in service was 0, but then went to the loft and removed the front cover, and below this PCB was a few drips of water.... basically the moisture should go down a tube that had become a bit gunked up (Despite recent servicing by me).

Ill try the IPA gently... it looks to be a simple circuit board. There are some new ones on eBay for £100 - £250!