Lead Plating,Lead Plating,Lead Plating,Lead Plating,Lead Plating
LEAD has been deposited from a variety of electrolytes, including fluoborates, fluosilicates, sulfamates, and methane
sulfonic acid baths. Fluoborate baths are the most widely used because of the availability of lead fluoborate and the
simplicity of bath preparation, operation, and stability. Fluoborate baths provide finer grained, denser lead deposits.
Fluosilicate baths, although less costly to use for large operations, are difficult to prepare for small-scale plating. They are
not suitable for plating directly on steel and are subject to decomposition, which produces silica and lead fluoride. Use of
sulfamate baths is almost nonexistent in the United States, because neither lead silicofluoride nor lead sulfamate is
available commercially. These salts must be prepared by the plater using litharge (PbO) and the corresponding fluosilicic
or sulfamic acids. Sulfamate baths are subject to decomposition, which produces lead sulfate.

The appearance and properties of lead limit its commercial use in electroplating largely to corrosion protection and
bearing applications-two fields in which the physical and chemical properties of lead render it unique among the
commercially plated metals. Lead has not been extensively electroplated because its low melting point of 325 °C (620 °F)
facilitates application by hot dipping. Electrodeposited lead has been used for the protection of metals from corrosive
liquids such as dilute sulfuric acid; the lining of brine refrigerating tanks, chemical apparatus, and metal gas shells; and
barrel plating of nuts and bolts, storage battery parts, and equipment used in the viscose industry.
Electroplated lead has been used for corrosion protection of electrical fuse boxes installed in industrial plants or where
sulfur-bearing atmospheres are present. Lead is also codeposited with tin for wire plating, automotive crankshaft bearings,
and printed circuits.
Nonporous lead deposits with thicknesses of 0.01 to 0.025 mm (0.4 to 1 mil) give good protection against corrosion,
although the coating may be subject to breaking during abrasion due to the soft nature of lead. Better mechanical
properties and improved durability are obtained with coating deposits with thicknesses greater than 0.025 mm (1 mil).
Depositing more than 0.08 mm (3 mils) of lead is relatively easy, in that a deposit of about 0.1 mm (4 mils) can be
produced in about 1 h at 2 A/dm2 (19 A/ft2) (Ref 1).

Process Sequence
Low-Carbon Steel. Lead can be plated directly on steel from the fluoborate bath using the following cycle:

· Degrease with solvent (optional)
· Alkali clean (anodic)
· Water rinse
· Dip in 10% fluoboric acid (Caution: Hydrochloric or sulfuric acid should not be used because they can
precipitate insoluble lead sulfate or chloride on the work in the event of poor rinsing)
· Water rinse
· Lead plate
· Rinse
Lead can be plated on steel from fluosilicate and sulfamate baths using the following cycle:
· Degrease with solvent (optional)
· Alkali clean (anodic)
· Rinse
· Dip in 5 to 25% hydrochloric acid
· Rinse thoroughly
· Dip in 30 to 75 g/L (4 to 10 oz/gal) sodium cyanide
· Rinse
· Copper cyanide strike
· Rinse thoroughly
· Dip in 10% fluoboric acid (see caution above)
· Rinse
· Lead plate
· Rinse
Copper. Lead can be plated directly on copper from fluoborate, fluosilicate, or sulfamate baths using the following
cycle:
· Alkali clean (anodic or cathodic/anodic)
· Rinse
· Dip in 10% fluoboric acid (see caution above)
· Rinse
· Lead plate
· Rinse
Fluoborate Baths
Lead fluoborate baths are prepared by adding the required amount of lead fluoborate concentrate and fluoboric acid to
water followed by peptone as the preferred addition agent.

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