Dynamic Immersion

SHMRC Beach Laboratory in Tuticorin Bay, India

Animated video of the dynamic machine in operation

The Poseidon Dynamic Test System

The Poseidon Dynamic Test System (PDTS) is a versatile platform that allows exposure of flat panels on a rotating frame in the middle of the sea. Supplied with electric power through an underwater cable from the shore laboratory (photo on left), the motors rotate the panels horizontally at various speeds ranging from 15 to 25 knots. The erosion rate as result of the fluid shear forces can be determined at each specific speed. The figure below shows the erosion of a self-polishing copolymer coating at different speeds.

The graph shows the erosion of coating at various velocities in the dynamic test system at month 3 of continuous exposure. The erosion rate is velocity dependent.

Although static immersion test is sufficient to measure the antifouling characteristics of a particular coating, it is not as reliable in determining the performance of the entire coating system. In many cases, panels that do well under static, fail when exposed to shear stress in the PDTS machine. Testing in advance enables reformulation or redesign of the top coat, primer and application procedures to meet customer expectations.

The comparison of same coating exposed for two months in both immersion tests. The difference in the results was compelling.


Poseidon Dynamic Testing System (PDTS) now makes it possible to simulate the erosion rate of marine coatings in a moving vessel. This new procedure enables simultaneous evaluation of the erosion rate at various fluid shear forces using flat panels. This system was presented in 2003 to the Society of Protective Coatings at its conference in New Orleans and at the Federation of Societies of Coatings Technology’s annual meeting in Philadelphia. For a PDF copy of this report, please click here.

In this procedure, flat metal panels are placed on a horizontal plane on a rotating disc immersed in the open sea, which causes erosion on the flat panel at various ship speeds of up to 40 miles per hour. The description of our marine research exposure stations and the dynamic testing system can be found in detail on the Poseidon website www.poseidonsciences.com.

The PDTS machine uses a standard flat steel panel supplied by ACT Test Panels, LLC (Michigan) with the following specifications:
Steel Panels
APR53743 ACT HRS – 04x06x071 Steel Grit Blast Both Sides; 2 Mil Profile (individually wrapped in VCI paper to prevent corrosion)
APR53940 Fiberglass 04x06x1/8″ Plain FRP – Smooth Finish
The panel can be purchased at the standard size of 4 inches by 6 inches (101.6 mm x 152.4 mm).
Sales: ACT Test Panels Technologies
273 Industrial Drive Hillsdale, MI 49242
Phone: 1-517-439-1485
The test panel may be coated on one or both sides and submitted to Poseidon for installation in the machine.

As shown in the figure (above), the position of the panel in the rotating disc will determine the relative velocities of the seawater. One panel can be used for each of the three (3) positions to obtain the full range of velocities possible and to conduct the evaluation in duplicate.

Combination of Dynamic and Static Immersion Testing
The PDTS machine offers the versatility of removing the panels at any client-specified period of exposure and subjecting the panel to static immersion. This enables the evaluation of the performance of the antifouling coating after a period of fluid shear stress and erosion rate. Ideally, multiple panels are subjected to the fluid shear stress of the PDTS machine and certain panels may be removed after various periods of time or at equivalent travel distance for static immersion.
Inspection Schedule
The test panels are inspected by removing the panel at a specified period of time (example: after 4 months) or upon reaching the equivalent distance (example: 10,000 miles).
Digital photographs via electronic mail of each panel (front and back side) are taken. Measurement of coating film thickness of metal panels is conducted when necessary. Measurements consist of three (3) positions along the midline of the panel on both sides. Since the fluid shear forces experienced by the panel vary depending upon the distance from the center shaft, the film thickness measurements represent erosion rate at three (3) different velocities for each panel.