Ni++ + H2PO2ˉ + H2O → Ni + H2PO3ˉ + 2H+

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H2PO2ˉ + H2O →H+ + HPO3ˉ + 2Hads

Ni++ + 2Hads → Ni + 2H+

2Hads → H2

H2PO2ˉ + H2O → H2PO3ˉ + H2

H2PO2ˉ + Hads → H2O + OHˉ + P

3H2PO2ˉ → H2PO3ˉ + 2OHˉ + 2P + H2O

TABLE I—Typical EN Bath Components

Component Function

Nickel SaltsSulfate, Sulfamate, Chloride

Source of nickel

ReducerHypophosphite

Reaction energy source for nickel to be available

for reaction. "The Chemical Rectifier".

ComplexorsCitric acid, Lactic acid, Malic acid

Allows controlled amount of nickel to be available

for reaction. Avoids a runaway reaction.

BuffersBorate, Acetate, Succinate

Inhibits dramatic pH changes

pH regulatorsAmmonium hydroxide

Potassium carbonate

Sulfuric acid

To adjust and maintain the operating pH

StabilizersMetallic - Pb, Sn, Mo

Organic - S Compounds

Plating rate control and prevent uncontrolled plate

out

Wetting Agentsbubble release and reduces pitting

Controls solution's surface tension and H2

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