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.
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
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.
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
||Annealed Yield Strength (psi)
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
Our Comprehensive Data Bulletin
• Chemical Compositions
• Mechanical and Physical Properties
• Shaft Tolerances
• Reference Tables
• Shaft and Bearing Selection
• Machining and Installation
• Marine Shafting Repair
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
*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
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)
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 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
(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 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
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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