S1205_ZINC_PROTECTORS.pdf

August, 1994

NOAA Standard Specification - S1205

ZINC PROTECTORS

Hull zincs (standard size 6"x12"x1¼") shall be installed on all steel, wood and aluminum hull ships. High purity zincs with cast-in strap should comply with specifications MIL-A-1801 and be attached in accordance with Figure 1.

The total number of 6"x12"x1¼" zincs installed on a single screw ship should equal the total underwater metallic area multiplied by 0.001; on twin screw ships this factor should be 0.0015.

Hull Plating - Steel Ships:

Zincs should be attached to the hull plating as close as practicable to and symmetrically about the propellers. Zincs should be attached in locations that will always be totally immersed. In addition, zincs shall not be attached to propeller shafts, rudder, skegs, stern tubes, strut arms or strut barrels. If practicable, the distance between adjacent zincs should not be less than 24 inches.

Wood Ships:

On wood ships, one 6"x12" zinc should be used for every 25 square feet of underwater metal area; however, a minimum of one zinc per rudder face, strut face and sea chest should be fitted.

Skegs where fitted and in metallic contract with a protected fitting, should be considered a part of the fitting.

For areas too small for a 6"x12" zinc, this size may be cut in half to 6"x6" or 3"x12" zincs may be used. Zinc shall be installed as shown on Figure I. On rudders, the zincs should be located outside of the propeller flow insofar as practicable. Zincs for struts should not be attached to the strut arm. Metallic contact may be made at the strut palm.

Straps of the zincs but NOT THE ZINC should be painted the same as the hull.

General Notes for Figure I

1. Install all zinc protectors in a fore and aft line where practicable.

2. Stud attachment for cast-in strap protectors are approved;

however, welding is preferred. When attachment is by studs, holes drilled in strap as shown. When welding straps to structure, ends may be cut off to within ¼" of bend.

Zinc Protectors S1205

3. After attachment, nuts shall be prevented from loosening by placing a cotter pin through the nut and stud, splitting the stud down its longitudinal axis, and peening over the stud, or by tack welding the nut in cast-in strap.

4. Where zincs are installed to the hull of a wood ship to protect the adjacent metallic structure, contact between the strap of the zinc and the protected structure may be made by welding or through the lag screw as shown in Detail A.

5. The protector will be able to withstand bending to a 15" radius on either axis. The protector shall be bent using a pyramidal roll, while hot (between 200° - 400°F).

List of Materials for Figure I

Pc.

No. Name of Piece Material Specification Remarks

1 Plate Zinc Protector Zinc MIL-A-18001 CL II, Type ZPN 2 Welding Stud, ½"-13NC-2 Steel Commercial Length to Suit 3 Nut, ½"-13NC-3 Steel Gal.Commercial 4 Lock Washer Steel Gal.Commercial 5 Cast-in Strap Protector Zinc MIL-A-18001 Cl I, Type ZHS 7 Stud, ½"-13NC-3 & 5 Steel Gal.Commercial Length to Suit 8 Zinc Oxide Paste Zinc Oxide 10 Cast-in Strap Protector Zinc MIL-A-18001 Cl I, Type ZHS 11 Lag Bolt, _" diameter Bronze Commercial Length to suit 12 Strap, 1¼"x3/16" Brass Commercial Length to suit