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Aqualoy is available in 4 different grades and is stocked in shaft sizes ranging from 3/4 inches to 8 inches in diameter with lengths up to 31-1/2 feet. Longer shafting is available for larger boats through precision rotary forging. This capability lets us manufacture Aqualoy propeller shafting with exceptional as-forged straightness up to 38 feet long and up to 15 inches in diameter.

Aqualoy Grades Available Include:
Aqualoy 22
Aqualoy 22 High Strength
Aqualoy 19
Aqualoy 17

Comparison of Marine Grade Materials with Standard ASTM Materials
The question is often asked what makes marine grade materials such as Aqualoy 19 or Aqualoy 22 better than a standard 304 or 316 stainless steels. The cost difference favors the standard materials so why would a user want the marine grade materials. Is this simply a case of marketing efforts creating a buzz to allow for higher pricing?

In order to understand the differences in the materials we need to first understand the environment in which the materials are expected to perform. Aqualoy 19 and 22 were created as specific upgrades to their standard counterparts in both strength and corrosion resistance. Table 1 shows the chemical composition of Aqualoy 19, 304, Aqualoy 22 and 316.

Grade Carbon Manganese Chromium Nickel Molybdenum Nitrogen
304 .06 1.5 18.5 8.5   .04
Aq 19 .06 1.8 19.5 8.5   .20
316 .06 1.5 16.5 12 2.1 .04
Aq 22 .03 5.0 22.0 13 2.2 .30

As you can see, the chemical compositions of the alloy pairs are different with Aq 19 having higher Mn, Cr and N than standard 304. Aq 22 also has higher Mn, Cr, N as well as higher Ni and Mo.

These chemical differences serve to improve alloy performance in two ways. First the increase in Mn and Cr increase the solubility of nitrogen which is important as nitrogen helps the alloys to attain higher strength. Secondly, the increase in Cr, Mo and N help to increase the pitting resistance equivalent number which is calculated as follows:

PREN = %Cr + 3.3 x %Mo + 16 x %N

Two of the most common forms of corrosion of stainless steel in marine environments are pitting and crevice corrosion. Typically alloys which are more resistant to one mechanism are more resistant to both. This equation has been used for many years to rank austenitic stainless steels and their relative resistance to pitting in chloride type environments such as sea water. Studies have shown that higher PREN’s correspond to increased resistance to pitting. If we are to calculate the PREN of our 4 alloys above one can easily see the superiority of the marine grades.

Grade Calculated PREN
304 19.14
Aqualoy 19 22.7
316 24.07
Aqualoy 22 34.06

From the chemistry modifications one would expect and indeed one does see improved corrosion resistance with the marine grades in marine environments.

As far as mechanical properties are concerned, the differences are also dramatic. In fact the original design criteria for Aqualoy 22 were to double the strength of 316 at the same time as the corrosion resistance was improved. As was mentioned earlier, the primary modifications to the chemistry was aimed at increased nitrogen content and when one looks at the annealed yield strength of the 4 alloys the improvements are obvious.

Grade Annealed Yield Strength (psi)
304 30,000
Aqualoy 19 50,000
316 30,000
Aqualoy 22 55,000

One further modification found on the marine grades is that in addition to the chemical modifications, there area also processing modifications which are designed to increase the strength dramatically above the annealed properties listed above. Depending on the size it is possible to increase the yield strength of both AQ 19 and AQ 22 in excess of 105,000 psi. This will allow more power to be transferred through marine grades of the same size when compared to their standard counterparts.

Download Our Comprehensive Data Bulletin

• Chemical Compositions
• Mechanical and Physical Properties
• Shaft Tolerances
• Reference Tables
• Shaft and Bearing Selection
• Machining and Installation
• Marine Shafting Repair

Click here to download our informative eBrochure.
(PDF format, 695kb)

Machine Charts Are Available – Order Yours Today

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Shaft Diameter and Safety Factor Calculator
A Safety Factor - Shaft Sizing - Bearing Spacing Program* is also available. WBM offers this simple program that enables customers to calculate safety factors and shaft diameters on their own PC. The program will operate on any version of Windows.

*Note: Shaft sizing calculation can be found in ABYC P6.

D is the shaft diameter
P is the rated horsepower
S.F. is the safety factor chosen
S is the yield strength in torsion
N is the shaft rpm
321,000 is a factor derived from converting horsepower to torque/balancing units

Note the yield strength in torsion is a calculated value from the tensile yield strength according to ABYC P6.

Click here to download this program now.
(ZIP format, 1.2mb)

Cathodic Protection
Aqualoy shafting materials are designed to offer the best combination of strength and corrosion resistance for their respective alloy groups. In order to insure long shaft life free from corrosion it is recommended that sacrificial anodes be used for all grades. For boats seeing only salt and brackish water Navy Grade zinc anodes are recommended. For boats used primarily in fresh water either magnesium or aluminum anodes are recommended. For boats seeing fresh brackish and salt waters aluminum anodes are recommended. It is important to note that in fresh waters zinc anodes will become ineffective in a very short period of time thus leaving all submerged metallic parts unprotected.

Aqualoy 22
Aqualoy 22 provides the best combination of corrosion resistance and strength for marine applications for 2” diameter and under. It is ideal for pleasure boats, considering that these boats spend much of their time docked where corrosion factors may be highest.

Aqualoy 22 has corrosion resistance better than any other boat shafting material, even better than most high-nickel alloys. Aqualoy 22 boat shafting provides yield strength in torsion up to 3.5 times that of most boat shafts now used, plus excellent toughness. Special processing controls provide consistent, high-quality 22 boat shafts that are precision straightened, centerless ground and polished to exacting marine tolerances. Aqualoy 22 is an austenitic alloy and is non-magnetic.

Superior Corrosion Resistance
Aqualoy 22 provides outstanding corrosion resistance. For example, in quiet seawater tests, Aqualoy 22 proved superior to type 316 stainless steel, long considered the standard for corrosion resistance in marine environments. After immersion for nine months, both alloys were covered with barnacles and other marine organisms. After cleaning, the 22 boat shaft was found totally unaffected, while type 316 exposed similarly suffered random pitting and crevice corrosion. Results of laboratory tests also demonstrate 22's superior resistance to different types of corrosion. One such test involved a 50-hour exposure in an acidified 10% ferric chloride solution. Finally, an 18-month test in actual seawater was conducted comparing 22 with Alloy 400 (Ni-Cu). Results showed that Aqualoy 22 was superior. Even though 22 is so highly resistant to corrosion, cathodic protection is recommended to avoid galvanic corrosion in salt and brackish water. Navy Grade zinc anodes, sufficient in number and properly installed, usually provide satisfactory protection.
(See Cathodic Protection)

Aqualoy 22 Available Sizes
Aqualoy 22 boat shafts are centerless ground and polished and precision straightened to meet the straightness requirements of Federal Specifications QQ-N-281, QQ-N-286 and ABYC*-P-6. 22 shafts are available up to 12 inches (304.8 mm) in diameter and up to 35 feet in length. Longer lengths are available by special inquiry.

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Aqualoy 22 High Strength
Aqualoy 22 High Strength provides the same corrosion resistance as the 22 but also offers the strength of the 17 in 2-1/4 inches through 6 inches in diameter. It is ideal for those vessels requiring higher strength shafts while maintaining the highest possible corrosion resistance available. Aqualoy 22 High Strength is an austenitic alloy and is non-magnetic.

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Aqualoy 19
Aqualoy 19 shafts have proven to be successful in several types of boats including sport fishing, and other pleasure crafts, as well as workboats where improved corrosion resistance is desired.

Aqualoy 19 boat shafting is a chromium-nickel stainless steel that is fully austenitic, nonmagnetic, and strengthened by a nitrogen addition. Corrosion resistance is superior to type 304 and better than Aqualoy 17 shafting. However, like type 304, Aqualoy 19 is susceptible to crevice attack when allowed to remain idle for prolonged periods in salt or brackish water. All shafts should have proper cathodic protection against corrosion. Navy Grade zinc anodes, sufficient in number and properly installed, usually provide satisfactory protection.
(See Cathodic Protection)

Aqualoy 19 has also proven itself in demanding service on shrimpers, crabbers, scallopers, and other fishing boats as well as on pleasure boats. Aqualoy 19 provides superior toughness and strength, and Aqualoy 19 shafts are competitive with most carbon steel shafts since the latter are fitted with sleeves and are frequently covered with fiberglass. With 19, there is no need for such sleeves or fiberglass, and smaller bearings and stuffing boxes can be used, resulting in lower overall cost.

Aqualoy 19 Available Sizes
Aqualoy 19 boat shafts are manufactured to meet the straightness requirements of Federal Specifications QQ-N-281 and QQ-N-286, and American Boat and Yacht Council* P-6, unless otherwise noted. They are available up to 12 inches (304.8 mm) in diameter and up to 38 feet (11.59 m) in length.

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Aqualoy 17 Shafting
Most crew boats in this country that service offshore drilling rigs are equipped with Aqualoy 17 shafts. So are shrimp trawlers...as well as many pilot boats, patrol boats and numerous other types of work craft. The reason for such wide acceptance in rugged service is simple: Aqualoy 17 shafts have proven themselves to have the finest combination of strength and toughness of any shafting material currently in use. When installed as original equipment, 17 shafts can be used in smaller diameters because of their extra strength. This means lighter struts and smaller bearings for less weight, less underwater drag and lower cost.

Aqualoy 17 is a precipitation hardening stainless steel, which has the highest strength, and hardness of all stainless steel boat shafting alloys over 2 inches in diameter. The composition of Aqualoy 17 has been carefully balanced to offer the maximum corrosion resistance possible in a heat treatable stainless steel. Corrosion resistance in seawater will approach type 304 but will be less than 19.

Although 17 has been used successfully for years it is more prone to pitting corrosion than the other marine alloys. Due to its composition the Aqualoy 17 is more prone to pitting and crevice corrosion than either Aqualoy 19 or 22. If the intended service conditions make the shaft vulnerable to either pitting or crevice corrosion we strongly recommend considering either the Aqualoy 19 or 22 products. Use of sacrificial anodes and elimination of stagnant water conditions have proven successful in limiting corrosion failures in this grade. We will provide Aqualoy 17 if specified by the customer but will not entertain claims for pitting or crevice corrosion since Aqualoy 17 is our least corrosion resistant offering.

Aqualoy 17 Available Sizes
Aqualoy 17 boat shafting is produced in sizes up to 12 inches (304.8 mm) in diameter and up to 38 feet (11.59 m) in length. Longer lengths are available by special inquiry.

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