Sodium Hydroxide

[Buzz]

Hi Folks,

I bought 5 litres of 70 TW Sodium Hydroxide last year just before the bad weather set in.
Never used it up till this weekend when I thought I'd try the solder mask removal trick with it.
I put one stick of SD-Ram in a plastic container and covered it with the Caustic.
Left it for two days now and nothing has occurred.

Can Sodiun Hydroxide lose its strength if left for long periods (8 months)?

Regards
Buzz

 

[Irons]

Sodium Hydroxide won't go bad. If left in the open, it will absorb Carbon Dioxide and slowly convert to Sodium Carbonate. It will also absorb moisture and cake up. Other than that, if you keep it in a sealed, non-corroding container, it should last many years.

 

[Oz]

Irons,

Just curious, is there a compound that has a greater affinity for C02 that would work as a preservative?

 

[Buzz]

Cheers Irons,

My Caustic has been sealed in a plastic container all this time, so I wonder why it's not attacking the solder mask?

Wonder if applying a bit of heat might help?
I'll give a go a bit later.

Regards
Buzz

 

[banjags]

there are certain types of solder masks that I have run into that sodium hydroxide will not touch. I have yet to come across something that will strip those boards. Supposedly methylene chloride will strip that solder mask but I have yet to find something that contains it in a strong enough concentration. Ans I have been a little hesitant as methylene chloride is a nasty chemical.

 

[goldsilverpro]

Every solder mask I've ever messed with crumpled in concentrated sulfuric acid. However, I sure didn't like the stink or the dangerous mess.

 

[Lou]

Methylene chloride is fairly cheap to buy at about $12/gallon 99% pure for paint stripping uses. Check ebay or a paint supply house. As far as toxicity goes, it's probably the least dangerous of the halogenated hydrocarbons because the main danger from dichloromethane is its narcotic effect.

 

[Irons]

Methylene chloride is fairly cheap to buy at about $12/gallon 99% pure for paint stripping uses. Check ebay or a paint supply house. As far as toxicity goes, it's probably the least dangerous of the halogenated hydrocarbons because the main danger from dichloromethane is its narcotic effect.

I used to use it on a daily basis for 9 months stripping optical fiber. Probable the biggest hazard is that it breaks down in the body into methyl alcohol and HCl. Methanol is not good for you in large doses.

There are mask filter cartridges that are rated to absorb it.

There are commercial stripping tanks that have a refrigerant coil above the solvent to condense the vapor and cause it to run back into the tank. We had a heated ulrasonic tank. You could put boards in that and they were stripped clean in a couple of minutes.

Dichloromethane is quite stable and easily recycled via distillation.

 

[gotgoldfever]

I have discovered that if I heat the caustic solution the solder mask comes right off. Otherwise it doesn't touch it.