A typical panel after 3 months in static immersion, with minor algae fouling.
Panel with heavy barnacle fouling, tube worm and the boring sponge, Cliona celata. There are 32 species of Cliona in the Mannar Barrier and they are responsible for considerable damage to pearl oyster beads.
A PVC panel totally covered by oyster fouling after 1 year of immersion.
Wood structures are heavily fouled by barnacles. Inside the submerged wood are channels created by Teredo worms.
Although there is a wide range of sophisticated testing available now to evaluate the performance of experimental paints under laboratory conditions, there is still no replacement for field testing of finished coatings in actual marine fouling environment. Static immersion remains a necessary step to validate the efficacy of coatings against fouling. Our primary test site for immersion testing is at SHMRC’s marine station in Karrapad Cove (Tuticorin Bay) in South India.
SHMRC Beach Laboratory
Why conduct immersion testing in Tuticorin Bay?
• Stable tropical environment with continuous barnacle fouling. The primary fouling organism is the barnacle, Balanus amphitrite amphitrite Darwin. This is also the most common fouling organism found in most parts around the world and likely distributed worldwide by seagoing vessels for many centuries. The seawater temperature remains above 200C all year and reach as high as 350C. The salinity remains oceanic, except during short monsoon season, when it drops precipitously (see figure below). However, barnacle fouling remains unaffected by the brief decline in salinity.
• In collaboration with SHMRC, the shore laboratory built in 2003 is dedicated exclusively to support the field research on biofouling.
• The research staff is comprised of marine biologists working on biofouling R&D.
• The location is within a protected cove and restricted from commercial use, thus avoiding damage on the platforms by commercial vessels.
• The adjacent Port of Tuticorin is the second busiest container port in India and therefore harbors the same fouling organisms that can be found in Singapore and similar warm water ports.
• Fouling is very aggressive. An unprotected surface becomes covered by juvenile barnacles within 2 weeks. A low copper coating, such as shown below, will foul within a month and show massive fouling from barnacles, algae and sponges as the immersion continues.
EXAMPLES OF FOULING CONDITION
The progression of fouling in Karrapad Cove on PVC rods coated with low level of cuprous oxide in the absence of co-biocides. By week 4, juvenile barnacles are already covering the entire surface. By week 8, green algae begin to cover the barnacles followed by sponges in the weeks that follow. Sponges occur seasonally, normally from October to November.
Static immersion testing is conducted on flat panels and PVC rods at Poseidon’s test centers. Please click on the link below to see a slideshow on how immersion testing is conducted on coated rods at Poseidon’s facility at the Sacred Heart Marine Research Center in southeastern India.
FOULING IN AQUACULTURE NETS
Near SHMRC is a shoreline with active aquaculture of macro-algae, usually Kappahycus, on floating nets by fisherfolk communities for income generation. Fouling on the nets is also a significant problem that reduces the yield and damage the value of the crop. Below are some of typical fouling organisms. Poseidon-SHMRC also conduct tests on antifouling systems for nets using this aquaculture area as a test environment.
Photos above show bryozoan and other foulers on aquaculture nets in the open ocean.
TOTAL IMMERSION TESTS
In total immersion, the panels are immersed below 2 ft from the surface. Fouling challenge tends to vary from site to site. It is therefore important to characterize the fouling conditions and the ideal depth of immersion. The data in the figure below show that fouling is heaviest at the 2 ft. depth. For this reason all total immersions are conducted at this level.
The graph shows the weight of fouling on PVC coupons at various depths after 2 months of immersion at Tuticorin bay. The photos demonstrates the degree of barnacle fouling on the panels at different immersion depth.
Panel specifications: Maximum width, 6 inches
Maximum length, 12 inches
(Panels of larger sizes can be accommodated but will be subject to surcharges for extra space)
Two mounting holes (1/8th inch diameter) on top left and right of the panel
Inspection Report: This is typically conducted on monthly, quarterly or biannual.
specifications. Please click here for an example of a
Fouling is most visible to the end users along the waterline. Many of the obvious coating failure occur along this interface because of UV damage and constant wave action. The waterline immersion test is designed to test the integrity of the paint from wave induced erosion and wave damage. In this test, half of the panel is submerged and the other half exposed to the surf and sun.
Photo on left shows waterline damage to the coating. Photo on the right shows barnacle fouling which appeared much earlier compared to total immersion test of the same coating that showed no fouling issues.
Panel specifications and inspection reports same as in total immersion.