# US 4,391,567 A · Corrosion preventing device for a marine propeller

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- Number: US 4,391,567 A
- Document ID: US4391567A
- Status: Granted
- Kind: A
- Application number: 06/259,811
- Filed: 1981-05-04
- Granted: 1983-07-05
- Earliest claimed: 1981-05-04
- Inventors: Dominick Ciampolillo
- Web page: https://patentgrep.com/patent/US4391567A

## CPC

- B63H 23/34: Propeller shafts; Paddle-wheel shafts; Attachment of propellers on shafts
- C23F 13/02: cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
- C23F 2213/31: Immersed structures, e.g. submarine structures
- B63H: MARINE PROPULSION OR STEERING (propulsion of air-cushion vehicles B60V1/14; specially adapted for submarines, other than nuclear propulsion, B63G; specially adapted for torpedoes F42B19/00)
- C23F: NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE (working metal by laser beams B23K26/00; desurfacing by applying flames B23K7/00; working of metal by electro-erosion B23H; producing decorative effects by removing surface material, e.g. by engraving, by etching, B44C1/22; electrolytic etching or polishing C25F); INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25

## Abstract

A corrosion preventing device is disclosed for mounting in sea water on an electrically conductive propeller shaft supporting a marine propeller composed of a metal having a first galvanic potential. The propeller is fastened to the shaft by an electrically conductive propeller nut and is in electrical contact therewith. The device includes an annular washer having a generally circular periphery, composed of a metal having a second galvanic potential not greater than the first galvanic potential, with a central hole concentric with the circular axis thereof through which the shaft may fit to enable an electrical conductive mounting proximate to the propeller nut, for serving as an electrolytic cathode of the device. The device further includes a generally toroidal anode having a circular periphery concentric with the axis, composed of a metal having a third galvanic potential greater than the first galvanic potential, cast about the periphery of the annular washer and exposed to the sea water, for serving as an electrolytic, sacrificial anode of the device. In this manner, the galvanic cell formed by the washer cathode and the toroidal anode maintains the propeller at a relative cathodic potential, thereby preventing the corrosion thereof in the sea water. The resultant device is less expensive to make, use and replace than those in the prior art because its component parts require no machining in their manufacture and the device is fastened to the propeller shaft with a simple jam nut.

## Claims

### Claim 1

A corrosion preventing device for mounting in sea water on an electrically conductive propeller shaft supporting a marine propeller composed of a metal having a first galvanic potential, the propeller being fastened to the shaft by an electrically conductive propeller nut, and in electrical contact therewith, comprising:
an annular washer having a generally circular raised rim about the periphery thereof forming a generally cup-shaped surface, composed of a metal having a second galvanic potential not greater than said first galvanic potential, with a central hole concentric with the circular axis thereof through which said shaft may fit to enable electrically conductive mounting proximate to said propeller nut, for serving as an electrolytic cathode of the device;
a generally torroidal anode having a circular periphery concentric with said axis, composed of a metal having a third galvanic potential greater than said first galvanic potential, cast about said rim on the periphery of said annular washer and exposed to said sea water, for serving as an electrolytic, sacrificial anode of the device;
said rim of said annular washer providing centripetal support to said torroidal anode to prevent the anode from mechanical disintegration during rotation at high angular velocities while the anode is in a state of protracted sacrificial corrosion.

### Claim 2 (depends on 1)

The device of claim 1, wherein said washer is composed of brass and said anode is composed of zinc.