Tecnoseal 00550 Series NACA Profile Shaft Collar Anode

Tecnoseal 00550 Series NACA shaft collar anodes provide sacrificial cathodic protection for marine propeller shafts measuring 19mm to 35mm. The range is available in zinc, aluminium and magnesium, with nine metric and imperial shaft sizes and a consistent 25mm axial width.

What Is This Shaft Anode Used For?

The Tecnoseal 00550 Series is fitted directly around an exposed marine propeller shaft. When correctly installed with direct metal-to-metal contact, the sacrificial anode forms part of the vessel’s cathodic-protection system.

The anode is designed to be consumed in preference to the immersed shaft and other connected underwater metal components, helping to reduce corrosion caused by galvanic and electrolytic activity.

Key Features

• Brand: Tecnoseal
• Product category: NACA-profile marine shaft collar anode
• Application: Propeller shafts and connected underwater metal components
• Shaft-size range: 19mm to 35mm
• Imperial sizes: 3/4in, 7/8in, 1in, 1 1/8in and 1 1/4in
• Available alloys: Zinc, aluminium and magnesium
• Width/height: 25mm across every variant
• Outside diameter: 55mm or 66mm, depending on shaft size
• Boat compatibility: Suitable for various vessel types using a matching shaft diameter
• Manufacture: Produced by Tecnoseal in Italy

Compatible Shaft Sizes and Part Numbers

• 19mm / 3/4in: 00550 zinc, 00550AL aluminium or 00550MG magnesium
• 20mm: 00550/1 zinc, 00550-1AL aluminium or 00550/1MG magnesium
• 22mm / 7/8in: 00551 zinc, 00551AL aluminium or 00551MG magnesium
• 25mm: 00552 zinc, 00552AL aluminium or 00552MG magnesium
• 25.4mm / 1in: 00553 zinc, 00553AL aluminium or 00553MG magnesium
• 28.6mm / 1 1/8in: 00554 zinc, 00554AL aluminium or 00554MG magnesium
• 30mm: 00555 zinc, 00555AL aluminium or 00555MG magnesium
• 31.8mm / 1 1/4in: 00556 zinc, 00556AL aluminium or 00556MG magnesium
• 35mm: 00557 zinc, 00557AL aluminium or 00557MG magnesium

Part-number note: The 20mm aluminium variant uses the Tecnoseal code 00550-1AL. The corresponding zinc and magnesium variants are 00550/1 and 00550/1MG.

Which Anode Alloy Should I Choose?

• Zinc: General selection for salt-water operation
• Aluminium: General selection for salt or brackish water
• Magnesium: General selection for fresh-water operation

Anode selection should also account for the vessel manufacturer’s specification, hull and shaft materials, the existing cathodic-protection system and local water conditions.

How Do I Select the Correct Size?

Measure the outside diameter of the propeller shaft and select the anode with an identical internal diameter. A 25mm shaft therefore requires part number 00552, 00552AL or 00552MG, depending on the required alloy.

• 19mm to 25.4mm shaft sizes: 55mm outside diameter
• 28.6mm to 35mm shaft sizes: 66mm outside diameter
• All variants: 25mm width/height

Do not select an anode solely by its external dimensions. The internal bore must match the shaft diameter to provide correct seating and direct electrical contact.

Alloy Standards and Manufacture

• Zinc: US Mil Spec. A-18001K
• Aluminium: US Mil Spec. A24779 SH
• Magnesium: US Mil Spec. A21412 SH

Tecnoseal manufactures its zinc, aluminium and magnesium sacrificial anodes at its foundry in Grosseto, Tuscany, and uses spectrometric testing to verify compliance with the applicable alloy specifications.