For this reason, they added more different products to the chromic acid; so that bore some enounces contenings: chromium sulfate boric acid, or borates - acetic acid - fuoridric fluoride, of chrome sodium fluoride - sodium acetate - sodium bisulfate different metallic sals like iron, copper, cobalt, nickel, aluminium, magnesium, cadmium, zinc, mercury, ecc.; except to count many other oxidant products, colloids, or others like potassium, peroxide, pepsine, peptone..
Almost all bodies or chemical products have been experimented, some to better pervasion power, the rest to increase the capacity, or the brightness.
Forasmuch we want to stay here in the chromium plating empiric contest and these different additives have not given a very tactile results, now into the shops «chromic acid» is the most used, with the added of 1% in pure sulfuric acid weight to 66 °B.
In chromic acid concentration can change into large limits, about from 250 to 400 liter-grams, and in parity the added of sulfuric acid will change in assonance from 2,5 to 4 grams-liter. But the chromic acid qualities in the business are often too much choppy, we shall to reduce the above mentioned sulfuric acid dose, either at the moment of a new bath formation, or when you add some important chromic acid quantities in an already working bath, and this to consider sulfate excess possible presence into the employed chromic acid.
When we prepared a new chromium plating bath, they exist some warnings: the chromic acid can be released about to 30 Kg concentration for 100Lt <
To longly admix the bath mass, because sulfuric- chromic acid mix was well uniform; this is necessary, considering the little percentual of this acid compared to the first.
This releasing act is too much unconsidered. The most people only "cut" the liquid, and not obtain the inner and uniform mix of the two elements; the sulfuric acid can't product its effect. From here the possibility to make wrongs, the bigger could be a new sulfuric acid added, and the consequent apparition of peculiar damages of this excess; it just because the bath was not well remixed at the beginning.
This observation derives from the first new chromium plating bath formation and its secondary alimentation; and for these last we have to put in evidence that the chromic acid addend has not to necessary be accompanied from the sulfuric acid in rapport of 1%.
It also will be important to treat a considerable number of objects after the chromic acid addend, and only in front of the presence of classic damages detecting the excess, or sulfuric acid flunk, you will make the necessary considered repair.
We should revisit this argument when we will arrive to the chromium plating damages. For a bath regular gear which gives the minimum of risks, the rapport of 1% between S04/Cr03 must be maintained; and if the deposit exam, or the bath work conditions don't give some clean signs to appreciate that this rapport is correct, it will need to recur to the analyses to have a correct indication.
In presence of a strong chromate excess we can lightly force the sulfuric acid dose; and this until the chromates elimination.
But this is a processing to avoid into the possibility; because after this elimination the acid excess will be stronger, with its consequences; and in this situation should better make a barite bath or to increase the chromic acid concentration.