plating is a portable process for accurate- plated  deposits  and anodized coat-onto localized areas (see Fig。 1)。 It offers portability, flexibility, and high-quality deposits and coatings。 It is approved  for use in military  and  com- Figure 1。 Brush plating can be accomplished in the field for repair operations。74975

mercial applications and is used for both OEM and repair operations。

Unlike stationary tank electroplating, brush plat- ing can be done anywhere in the shop or out in the field。 Brush plating requires very small volumes of solution, usually only 1 or 2 gallons, a lightweight rectifier, and some tooling。 With this minimal equip- ment, brush plating and anodizing are easily carried out at the jobsite。

This flexible process works when other methods of applying metals and coatings won’t。 Localized areas on parts too large or too difficult to mask for con- ventional tank plating are easily masked and then plated or anodized。 Unlike welding and flame spray, which deposit large amounts of material quickly and then require a finish machining or grinding opera- tion, brush plating permits accurately controlled buildups ranging from a few millionths of an inch to thirty thousandths of an inch thick or more。 In many cases no finish machining operation is required。 Additionally, brush plating is a room-tem- perature process that does not develop the heat causing distortion associated with welding and flame spray。

Brush-plated deposits are applied at much faster rates than those achieved in tank plating。 With proper surface preparation the quality of the deposit and adhesion are equivalent or superior to good tank plating practice。 Most brush-plating deposits have a dense, pore-free, and uniform crystalline structure like the sulfamate nickel deposit shown in Figure 2。 The adhesion is sound as illustrated in the

Figure 2。 Photomicrograph  of brush-plated nickel deposit。

photomicrograph (Fig。 3) taken on a panel bent back and forth until it fractured。 The force applied exceeds the yield and tensile strength on a microlev- el for  the base  material。

Figure 3。 Sound adhesion is confirmed by failure in the sub- strate and not at the interface。

Metal Finishing

Thble I。 Specifications for Brush Plating and Anodizirig

AMS  2451  -  1 through /11 Brush  Plating

MIL-STD 865 Selective (Brush Plating)

  Electrodeposition

is actually pumped through a series of small, uni- formly spaced holes in the anode to evenly cover the work  area。

A portable  power pack (rectifier) provides a  source

MIL-STD 2197 ASH)

MIL-A-8625

Brush Eectroplating on Marine  Machinery

Chromic (Type I), Sulfuric (Type III, Hard Coat (Type III), Anodizing

of direct current for all the processes。 The power pack has at least two leads。 One lead is connected to the tool and the other is connected to the part being finished。

The direct current supplied by the power pack is used  in  a circuit  that  is completed  when  the tool is

The manufacturers of brush plating equipment generally offer a number of plating solutions for each of the more important metals。 One reason  for this is to offer  a choice  in properties。  For    example,

one user may want a hard, wear-resistant nickel while another wants an impact-resistant, ductile coating。

Since the ductility of metals, whether wrought, cast, or plated, generally decreases with increasing hardness, it is impossible to meet both requirements with a single solution。