N15class Posted March 7, 2012 Share Posted March 7, 2012 Hi I need to clean up a brass and nickle kit. Also remove a little paint. I have been thinking of costic soda which is easy to get here in Brazil. I know there have been sugestions of citric acid and vinigar. Is costic soda going to be to strong? Has anyone any experience of it. Also what does it do to whitemetal? Thanks in advance Peter Link to post Share on other sites More sharing options...
Kenton Posted March 7, 2012 Share Posted March 7, 2012 I'm pretty certain it will blacken both white metal and brass, though it probably depends on the concentration, time immersed and temperature. Also beware of how the kit has been built. If not soldered it may make any glue brittle. Link to post Share on other sites More sharing options...
billbedford Posted March 7, 2012 Share Posted March 7, 2012 You need an acid to bright dip brass and nickel silver. The traditional 'cheap' method was with a saturated solution of salt in vinegar. If you can get domestic cleaners for removing limescale from kettles etc that will work just as well or better. Link to post Share on other sites More sharing options...
N15class Posted March 7, 2012 Author Share Posted March 7, 2012 You need an acid to bright dip brass and nickel silver. The traditional 'cheap' method was with a saturated solution of salt in vinegar. If you can get domestic cleaners for removing limescale from kettles etc that will work just as well or better. I know about Viacal etc, I have a bottle here. You just can't buy limescale products here. So I am louthed to use it on a major clean, and save it for painting pre wash. I will have a look at salt and vinigar. What is the salt added for? Link to post Share on other sites More sharing options...
billbedford Posted March 7, 2012 Share Posted March 7, 2012 Salt + Vinegar produces hydrochloric acid. Link to post Share on other sites More sharing options...
N15class Posted March 7, 2012 Author Share Posted March 7, 2012 Salt + Vinegar produces hydrochloric acid. I knew I should of paid more attention at school. Link to post Share on other sites More sharing options...
Kenton Posted March 7, 2012 Share Posted March 7, 2012 Salt + Vinegar produces hydrochloric acid. I am afraid that is not true. Basic chemistry here we have a weak organic acid in the vinegar - as acetic acid CH3COOH and we have a strong salt sodium chloride NaCl.  In any solution sodium chloride is completely ionised to form sodium Na+ and chloride Cl- ions. Acetic acid is a fairly weak acid and forms relatively few hydrogen H+ and acetate CH3COO- ions. All of these ions remain in original proportion and NO reaction occurs to form any other compound. It would require considerable additional energy to generate hydrochloric acid which would be transient as it would react immediately with the remaining sodium ions. The preferred state is always going to be sodium chloride even in saturated solution. However, the neat trick is the release of the hydrogen ions these are free to react with the oxidised metal surface reducing the oxide back to the pure metal. The sodium chloride maintains a high ionic strength for the process and may well help to prevent reoxidation. This will not happen if you replaced the mix with a hydrochloric acid. Hydrochloric acid will react with most metals to produce chloride salts on the surface, in some but not all cases these are insoluble. It has been a few decades since my chemistry degree, but I think that is how it goes. I think it goes in Chemistry teacher speak - "A weak acid cannot displace a stronger acid." "Or given a balance of ions they will form a strong salt bond in preference to any other." Link to post Share on other sites More sharing options...
billbedford Posted March 7, 2012 Share Posted March 7, 2012 That sound a lot better that -- well the salt makes it work:-) Link to post Share on other sites More sharing options...
Guest Natalie Graham Posted March 7, 2012 Share Posted March 7, 2012 Salt + Vinegar produces hydrochloric acid. How about cheese and onion? Link to post Share on other sites More sharing options...
Kenton Posted March 8, 2012 Share Posted March 8, 2012 How about cheese and onion? No, I think that will only produce wind. Link to post Share on other sites More sharing options...
Fat Controller Posted March 8, 2012 Share Posted March 8, 2012 You could always do what the tinplate works in Llanelli used to do into the 1950s- use urine! My great-aunt, who kept a pub, told me there used to be people who would come round every couple of days and collect the urine from the pub toilets. The pickling vats built up a layer of saltpetre over time- very interesting to teenagers who had done a modicum of chemistry... My uncle, who was in the Welsh Guards,told me that the same liquid, left overnight in new boots, would soften them. Naturally, you had to remember to empty them before morning parade. If you're slightly queasy about collecting your matinal micturations, then you may find that you are able to obtain dilute hydro-chloric acid from a local hardware shop or swimming-pool supplies company- it's used to adjust the pH. I get mine from Auchan hypermarket in Coquelles, and use it to remove limescale. Link to post Share on other sites More sharing options...
Horsetan Posted March 8, 2012 Share Posted March 8, 2012 ..... use urine! My great-aunt, who kept a pub, told me there used to be people who would come round every couple of days and collect the urine from the pub toilets. The pickling vats built up a layer of saltpetre over time- very interesting to teenagers who had done a modicum of chemistry... My uncle, who was in the Welsh Guards,told me that the same liquid, left overnight in new boots, would soften them. Naturally, you had to remember to empty them before morning parade. I'm sure the process was p*ss-easy. Link to post Share on other sites More sharing options...
N15class Posted March 8, 2012 Author Share Posted March 8, 2012 Well I have tried the vinegar and salt. It works but as said it is very gentle. I am not sure how long it is ment to be left pickling? But with a combination of alcohol to remove paint, vim and tooth brush to remove grease, and pickling I was quite please with the result. I my of been impatient, and not let the solution do it's work? Link to post Share on other sites More sharing options...
Kenton Posted March 8, 2012 Share Posted March 8, 2012 How long? will depend on a few unknowns - how badly it needs cleaning, the temperature of the solution, how "dirty" the solution has become, residual paint, agitation of the "pickling" bath (a gentle rocking motion would probably be best); and time - I would try progressive steps of 4hr,8hr,12hr,24hr expecting an overnight to work. Link to post Share on other sites More sharing options...
N15class Posted March 8, 2012 Author Share Posted March 8, 2012 The next querry what is the best think to nutralise the acid with? Baking powder I would of thought? Can I get it here? The loco comes out of acid niceand bright but no matter how much rinsing in running water it tarnishes as it dries. Any thoughts? Link to post Share on other sites More sharing options...
Fat Controller Posted March 8, 2012 Share Posted March 8, 2012 The next querry what is the best think to nutralise the acid with? Baking powder I would of thought? Can I get it here? The loco comes out of acid niceand bright but no matter how much rinsing in running water it tarnishes as it dries. Any thoughts? Not baking powder, which is a mixture of bicarbonate of soda and citric acid- you should be able to get bicarbonate of soda and washing soda fairly easily. If using the latter, do wear gloves, or you'll have lovely red hands.. Link to post Share on other sites More sharing options...
N15class Posted March 8, 2012 Author Share Posted March 8, 2012 Trust me, I was thinking of bicarbonate of soda, as I was typing baking powder. Link to post Share on other sites More sharing options...
Kenton Posted March 8, 2012 Share Posted March 8, 2012 Referring back to my previous lesson on chemistry - it is no more an acidic solution than the vinegar you dispense on your fish and chips. You need do nothing more than you would after eating your fish and chips - wash it thoroughly in water. Acetic acid is not toxic and neither is salt unless we are being silly. Though I would not use the dirty mix on my fish and chips. Remember it is NOT hydrochloric acid. Link to post Share on other sites More sharing options...
N15class Posted March 8, 2012 Author Share Posted March 8, 2012 Referring back to my previous lesson on chemistry - it is no more an acidic solution than the vinegar you dispense on your fish and chips. You need do nothing more than you would after eating your fish and chips - wash it thoroughly in water. Acetic acid is not toxic and neither is salt unless we are being silly. Though I would not use the dirty mix on my fish and chips. Remember it is NOT hydrochloric acid. Can you say why this comes out of the rinse nice and clean and then by the time the water has dried it is tarnisned again. I thought it needto nutralised. Link to post Share on other sites More sharing options...
Kenton Posted March 8, 2012 Share Posted March 8, 2012 Can you say why this comes out of the rinse nice and clean and then by the time the water has dried it is tarnisned again. I thought it needto nutralised. It has a lot to do with the stuff we breathe - the atmospheric oxygen simply re-oxidises (tarnishes) the bare metal.The cause is actually a little more complex than that. The H+ ions at the metal surface have a certain activation effect and the new shiny and exposed metal surface is very prone to oxidation (rusting in the case of ferrous content). This should be a relatively slow process if the vinegar has been thoroughly washed off. The metal is in very much the same state as when it comes out of the etching bath. It should be either kept wet (under water) or completely dried and kept in a moisture free atmosphere. - that is why you should see all good kits packed with a desiccant sachet. You can also coat as soon as possible with your preferred undercoat, assuming you have just cleaned for painting. Link to post Share on other sites More sharing options...
N15class Posted March 11, 2012 Author Share Posted March 11, 2012 Maybe I need to use the hair dryer to dry it quickly. At the moment it is for construction and soldering. It would notbeaproblem for painting. I have gone over the loco body with a nylon brush vim and a mini drill. This stay brighter longer than the pickling. Iwas hoping that pickling would be of greater benifit. When I was in the clock trade we used a pickle that kept a lovely bight matt finish on the brass that lasted a few weeks, if it was not laquered. Link to post Share on other sites More sharing options...
JeffP Posted March 11, 2012 Share Posted March 11, 2012 I once cleaned up an old miner's lamp, and was told to soak it in Coca-Cola. It seemed to do the trick, all parts coming up nice and clean, if not shiny. But it WAS in the bucket for a good few days. Link to post Share on other sites More sharing options...
billbedford Posted March 13, 2012 Share Posted March 13, 2012 Can you say why this comes out of the rinse nice and clean and then by the time the water has dried it is tarnisned again. I thought it needto nutralised. Rinse it with the hottest water you can stand. The quicker the the model dries the less water staining you will get. A lot depends on what is in you local atmosphere, sulphur is not usually a good idea. Don't use washing soda for neutralising, it tends to turn the brass black. Link to post Share on other sites More sharing options...
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