Me vs NiCad battery damage on PC boards

[Sridhar Ayengar]

Chuck Guzis wrote:
> On 2/1/2006 at 1:56 PM Joe R. wrote:
> 
> 
>>  I've seen the stuff you're talking about. Even after you clean off the
>>blue-green corrision the copper is black and solder won't stick to it. I
>>expect the black is due to copper oxide. You need to remove it by treating
>>it with some kind of acid that will form a water soluable salt with
> 
> copper.
> 
>>I expect dilute sulfuric acid may be the best. That's what they use to
>>clean copper circuit boards prior to assembly as well as  copper items
>>prior to electroplating, etc.  
> 
> 
> The brass instrument folks use muriatic (hydrochloric)  acid or sulfamic
> acid for cleaning.  Still as dangerous as sulfuric when it comes to getting
> it lodged in nooks and crannies (and if this is an old board, it can even
> get wicked under traces), but easier to get because they're not on the list
> of reagents that explosive or drug makers use.  Another chemical that may
> work is thiourea. 

Does one need to use a strong acid for this cleaning?  Can one use a 
concentrated weak acid instead?

Peace...  Sridhar