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.
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.
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
TOTAL IMMERSION TESTS
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
Inspection Report: This is typically conducted on monthly, quarterly or biannual.
specifications. Please click here for an example of a
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.