Tecnoseal 00500USA Series USA Egg Type Shaft Anode

Tecnoseal 00500USA Series USA-type egg-profile propeller-shaft anodes are split, bolted sacrificial collars for exposed marine shafts from 19mm (3/4in) to 50.8mm (2in).  Match the shaft diameter, axial length, outside-diameter clearance and alloy before ordering.

What Is This USA-Type Shaft Anode Used For?

The two-piece anode clamps directly around an exposed propeller shaft. With clean metal-to-metal contact, it forms part of the vessel's cathodic-protection system and is consumed in preference to the shaft and other electrically connected underwater metal components.

The USA-type egg profile is a distinct Tecnoseal shaft-anode family. It should not be treated as interchangeable with standard egg-type, UK-type, NACA-profile or limited-clearance collars solely because the internal bore appears similar.

Key Features

• Brand: Tecnoseal
• Product category: USA-type egg-profile marine propeller-shaft anode
• Model range: 00500USA to 00514USA, including M, AL and MG variants
• Shaft-size range: 19mm / 3/4in to 50.8mm / 2in
• Available shaft sizes: 16
• Available alloys: Zinc, aluminium and magnesium
• Total selectable variants: 48
• Mounting: Split, bolted clamp around the shaft
• Application: Exposed marine propeller shafts and electrically connected underwater metalwork
• Manufacture: Made in Italy by Tecnoseal

Available Shaft Sizes and Part Numbers

• 19mm / 3/4in: 00500USA zinc, 00500USAAL aluminium or 00500USAMG magnesium
• 22mm / 7/8in: 00501USA zinc, 00501USAAL aluminium or 00501USAMG magnesium
• 25mm: 00502USA zinc, 00502USAAL aluminium or 00502USAMG magnesium
• 25.4mm / 1in: 00503USA zinc, 00503USAAL aluminium or 00503USAMG magnesium
• 28mm: 00504USA zinc, 00504USAAL aluminium or 00504USAMG magnesium
• 28.6mm / 1 1/8in: 00505USA zinc, 00505USAAL aluminium or 00505USAMG magnesium
• 30mm: 00506USA zinc, 00506USAAL aluminium or 00506USAMG magnesium
• 31.8mm / 1 1/4in: 00507USA zinc, 00507USAAL aluminium or 00507USAMG magnesium
• 35mm / 1 3/8in: 00509USA zinc, 00509USA/AL aluminium or 00509USAMG magnesium
• 38.1mm / 1 1/2in: 00510USA zinc, 00510USA/AL aluminium or 00510USAMG magnesium
• 40mm: 00511USA zinc, 00511USAAL aluminium or 00511USAMG magnesium
• 44.5mm / 1 3/4in: 00511MUSA zinc, 00511MUSAAL aluminium or 00511MUSAMG magnesium
• 45mm: 00512USA zinc, 00512USAAL aluminium or 00512USAMG magnesium
• 48mm: 00512MUSA zinc, 00512MUSAAL aluminium or 00512MUSAMG magnesium
• 50mm: 00513USA zinc, 00513USAAL aluminium or 00513USAMG magnesium
• 50.8mm / 2in: 00514USA zinc, 00514USAAL aluminium or 00514USAMG magnesium

Part-number note: Tecnoseal uses a slash in the aluminium codes 00509USA/AL and 00510USA/AL. The 44.5mm and 48mm variants use the additional letter M in the base code.

How Do I Select the Correct Size?

Measure the shaft outside diameter accurately with callipers and select the anode with the identical internal bore. Then confirm the axial space and outside-diameter clearance around the installed collar.

• Exact shaft bore: Do not substitute a nearby metric or imperial size. A 25mm shaft and a 25.4mm / 1in shaft require separate variants.
• Axial length: Confirm that the shaft has enough exposed length for the selected anode.
• Outside diameter: Check clearance from the stern tube, shaft bracket, hull, rope cutter and nearby fittings.
• Rotational clearance: Rotate the shaft by hand where safe after installation to confirm that the complete collar clears surrounding components.
• Profile family: Match the USA-type geometry and original part number rather than selecting by bore alone.
• Alloy: Select the alloy specified for the vessel, connected metals and operating water.

The 44.5mm and 45mm sizes, and the 50mm and 50.8mm sizes, are separate products. Do not treat the nominal inch and metric options as interchangeable.

Which Anode Alloy Should I Choose?

• Zinc: A conventional selection for salt-water operation where zinc is specified.
• Aluminium: Generally selected for salt or brackish water and lower in mass than an equivalent zinc casting.
• Magnesium: Generally selected for fresh-water operation and normally unsuitable for prolonged salt-water use because it may be consumed too rapidly.

Use the alloy specified by the vessel, shafting or equipment manufacturer and keep the selection consistent with the existing cathodic-protection system. Water salinity, connected metals, shore-power arrangements, bonding condition and stray-current activity can alter the correct choice.

Installation and Maintenance

Clean the shaft to bright, bare metal where the anode will sit. Position both halves squarely around the shaft and tighten the fasteners evenly in stages so the anode clamps securely without rocking or leaving an uneven joint.

Do not apply paint, grease, sealant or insulating compound between the anode and shaft. Direct electrical contact is required. Do not assume that replacement fasteners are included unless the selected product offer expressly states this; the fastening arrangement varies by size.

Inspect the anode during scheduled servicing and after prolonged operation in a different water type. Replace it when substantially consumed, cracked, loose or no longer able to clamp securely. Investigate unusually rapid or uneven consumption rather than fitting a larger anode without identifying the cause.

Alloy Standards and Manufacture

Tecnoseal manufactures zinc, aluminium and magnesium sacrificial anodes at its foundry in Grosseto, Tuscany, and checks alloy composition using spectrometric measurements against the applicable material specification:

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

Frequently Asked Questions

• Can I fit a larger bore and tighten it down? No. The internal diameter must match the shaft so the anode seats correctly and maintains reliable electrical contact.
• Is a 25mm anode suitable for a 1in shaft? No. Select the separate 25.4mm / 1in variant.
• Are 44.5mm and 45mm interchangeable? No. They use separate Tecnoseal part numbers and must be matched to the measured shaft.
• Are 50mm and 2in interchangeable? No. A 2in shaft is nominally 50.8mm and uses the 00514USA family.
• Is this the same as a standard or NACA-profile shaft anode? No. Match the USA-type family, complete dimensions and original part number.
• Are fastening bolts included? Do not assume so unless the individual product offer specifically confirms included hardware.
• Can the anode be painted? No. Keep the sacrificial surface and shaft-contact faces free from paint and insulating coatings.
• Can I mix zinc, aluminium and magnesium on the same vessel? Follow the vessel or equipment manufacturer's cathodic-protection specification rather than mixing alloys without technical guidance.

Specifications