De-gassing and fluidising

[geoff_p]

I've read in various places about degassing with Sodium Chloride (common salt) and using Sodium Carbonate (washing soda) to fluidise my ali melts.

Well, even I can find salt in the kitchen, but tracking down washing soda has proved much more difficult. My command of Thai is not good enough to explain that, in the days before modern detergents, people used it for their laundry. Much head-banging-on-the-wall has ensued.

In desperation, I bought a small packet of stain-remover - Hygiene Zuper O2 (a Thai product so all the destructions are in Thai).

With the aid of a magnifying glass, I spotted the composition written in English:
Sodium Carbonate Peroxyhydrate 50%;
Sodium Carbonate 39%
Sodium Lauryl Sulphate 6%
Sodium Lauroyl Sarcosinate 0.5%

On the basis that it contain about 90% of some-form-of-washing soda, I'll give it a try.
Interestinly, it is coloured blue, as were the commercial degassing tablet I had a zillion-years ago, though in this case it is probably just some Blue-whitener.

Geoff

[dallen]

might turn your aluminum blue

[geoff_p]

Or the air!

[HT1]

Calcium hypochlorite should be all you need. and if memory serves, that is exactly what the old blue pucks where. you can order it in a granular form, from any chemical supply house, probably requires ground shipping since it is corrosive. It will bleach your clothes wonderfully also, so dont spill any of it
old school pool cleaning chemical was just Calcium hypochlorite. but it is hard to find nowdays, but it is till out there

V/r HT1

[bunyip]

Geoff, the washing soda I manage to get at the supermarket here in Aus is a white powder & the only ingredient it lists is Sodium Carbonate.Have heard Lite salt which has a lot less sodium chloride & a fair wack of "potassium chloride" is usefull for degassing aluminium.Perhaps you may be able to get that over there.Cheers.

[Harry]

AFAIK lite salt is used for fluxing not degassing. This would be applied to the surface of the melt where degasser is applied at the bottom so the bubbles produced come up through the melt and attach to gas in the metal. I dont often use flux and just skim off the top before pouring, this 'wastes' some metal that would otherwise be released but I just save these skimmings to either return to the recycler or scrap back into ingots later. It just seems to me a lot less hassle and % of loss not enough to be of concern.

On degassing I have been using tablets from my foundry supplier that are supposedly the same stuff BCS sells. It generates plenty of bubbles but I am still not happy with size of bubbles and would like something much smaller. There is a distinct chlorine smell which is also an issue in keeping ventilation up to task which should be anyhow for combustion fumes. I am going to try nitrogen as soon as I find a good bubbler, have a 75/25 mix for my mig welder which I believe will work fine. Just want to try and eliminate the last few tiny bubbles causing porosity I see in my milled castings.

[geoff_p]

Somewhat off-track: t'other day I thought to do just what Harry described here - put some of the skimmings back into the pot.
Unfortunately, they just didn't look to be melting at all, so that there was no sign of that magic, metallic gleam even though there had been plenty of 'real' metal in the initial melt.

Then I found the bloody big hole in the bottom of the pot! All the 'metallic gleam' was now in the ash-pit below my fire.

Moral of the story? Don't trust Asian-made stainless-steel cookware to actually 'be' stainless-steel. My saucepan (brand-new only one week ago) was in fact just chrome-plated crap! Ooooh, I wish I could buy a proper crucible here in Thailand.

Geoff

[Rasper]

Surely you have foundries there, and foundry suppliers. I live in Mexico, and we have more foundries, and suppliers, just in Mexico City, than probably exist in all of the United States, Canada, and Europe combined. Foundries thrive in the less rich countries. There must be guys casting metal and making their own crucibles in every town in Asia.

Richard

[geoff_p]

Hi Richard, Yes, I would have thought so, too.

Months ago, I wrote to the Thai Foundries Association but, in common with most Thai businesses, communicating with farang (English-speaking foreigners) is a last-resort and farangs should preferably be ignored.

Strictly-speaking, what I am doing is illegal anyway: foreigners are not allowed, by law, to do anything for themselves. Rather they should spend their money paying Thais to do/make 'it' for them.

And that, I hear you say, becomes a circular argument. If they won't communicate, how can I give them work?

Bangkok and its provinces certainly do have foundries but it's a bloody big, sprawling city (not too unlike Mexico City, I would think) and I don't fancy driving around it hoping to find a foundry 'by chance.' I would sooner make contact first.

Geoff