A fairly wide application of an iron-nickel alloy, otherwise called Invar, required a fairly simple method of obtaining it.
Many people do not know that the production of such an alloy is performed in a galvanic way.
The alloy of iron with nickel is called Invar. It has found wide application in precision instrumentation, namely in the manufacture of geodetic wire, all sorts of standards of length, details of clocks, altimeters, lasers, etc. One of the easiest ways to produce an iron-nickel alloy is galvanic.
The problem of the galvanic method of obtaining an iron-nickel alloy and the way to eliminate it
Comparing the thermodynamic characteristics of bothMetals, it seemed to scientists that it was easy to get an alloy. In practice, everything turned out to be directly opposite, since the reaction involves a by-product oxidation process - iron passes from the bivalent state to the trivalent state. This reduces the current yield of the target product and worsens its physical characteristics, and sometimes completely eliminates them. This problem can be solved by introducing into the electrolyte a complex additive consisting of amines and organic acids and forming poorly soluble compounds with ferric iron. As a result, the elasticity of the sediment improves. Mixing of the electrolyte is used to reduce the spread along the thickness of the precipitate.
Electrolytes for applying an iron-nickel alloy
The sulphate electrolyte for obtaining an iron-nickel alloy has the following composition:
Component ;;;; g / l
Iron sulphate ;; 2
Nickel sulfate ;; 60
Boric acid ;;; 25
Sodium lauryl sulfate ;; 0.4
The operating mode of the electrolyte is pH = 1.8-2
Temperature - 40-50 degrees Celsius
The cathode current density is 3-7 A / dm2
Anodes can be usedMetallurgical alloys of iron and nickel or plates of nickel and iron. If you use a plate, then you need to maintain the ratio of areas. The area of the nickel plate should be three times larger than the iron plate.
The hydrochloric acid electrolyte for obtaining an iron-nickel alloy has the composition:
Component ;;;; g / l
Iron chloride ;; 150-160
Nickel chloride ;; 2-4
Acid, hydrochloric ;;;; 2-4
Electrolyte working mode:
Temperature - 50 degrees Celsius
The cathode current density is 10 A / dm2
The disadvantage of this electrolyte is the saturation of hydrogen products, if carried out electrolysis by a current greater than this. This increases the fragility of metals.
Sulfamate and fluoroborate electrolyte of the alloyIron-nickel. This electrolyte provides a high rate of deposition, minimal internal stresses and elasticity of the sediment. But because of the complexity of the composition and the high cost of components, it has not found wide application in the industry. Therefore, the article does not list its composition.