fume control

[lazz3125]

having recently started anodizing at home, with the normal startup woes that seem to beset any new project, i am left with one slight problem to solve. I have the acid tank setup with 1 bottle of fume control chemical added but without the foam blanket present unless the surface is agitated, ie when i use a device for checking the SG. Any suggestions as to causes and or cures would be welcome


Regards, lawrence

[M_D]

I use it and it works well to control the fumes, but it doesn't foam in my tank which uses a recirculating pump for agitaion. If it is supposed to foam that's news to me. Maybe it does if air is used for agitation?

[mcaswell]

This is not a foam system. It's more like an 'oil' that floats on the surface

[Fibergeek]

Can I ask why you are checking SG (specific gravity)?

[lazz3125]

Thanks for the replies, I am now enlightened. Fibergeek: the SG came into the equation as i had read that an SG of around 1150 is about right for type II anodising. I checked it, found it a lttle high and supposed that it may be the cause of my non existant foam, no other reason.

Thanks again, Lawrence

[Fibergeek]

As you anodize, very small amounts of aluminum are dissolved in the electrolyte. This is normal and expected. This aluminum content in the electrolyte will throw off SG readings, making them look higher since the dissolved aluminum is heavier than sulfuric acid. This makes SG readings worthless as soon as some anodizing takes place.

If you're using commercial battery acid as your source of sulfuric acid (most here do) a mixture by VOLUME of 1 part battery acid to 3 parts distilled water forms the LCD electrolyte. If you want the stronger traditional mixture, use 1 part battery acid to 1 part water, this is very close to the 165g concentrated sulfuric acid per liter of water by WEIGHT traditionally used. I don't know what the SG is of either mixture and don't much care. In practice, with either mixture if you use reasonable care measuring your quantities using an ordinary measuring cup you will be fine. The ratios are not very critical. Use only new, unused battery acid of course.

I don't think acid concentration is the cause of your foaming, Like Caswell says, it isn't supposed to foam. Perhaps you put in way too much mist suppressant (the correct term) follow the mixing directions on the bottle, or maybe you have introduced another contaminant in your tank.