Tracking corrosion in sea water can be a challenging task
A tennis pro from Florida went to the Dominican republic for vacation. He was artying and having a great time. One night he started acting kinda weird and paranoid and the next day he went missing. Approximately 8 weeks later his wallet was found on the beach in the DR. All his credit cards, ID, and about 400 in chash were in it. The chash was worn out and the chip on the cards was extremely corroded. Some of the graphics on the PVC card were coming delaminated as well. His family hired a private detective to no avail. They sent me the wallet and asked if it had been in the water. I took everything out and took pictures. I found some sand/ crumbs in the wallet and put them under a scanning electron microscope with EDS. The crumbs were calcium rich sand and with some whole and fragmented diatom frustules. The family then asked how long the wallet had been in the water. That’s nearly impossible to tell. I designed an experiment to try to help. I took some credit cards and sunk them to the sea floor and took photographs periodically. After 7 weeks, there is no evidence of corrosion on any magnetic strips or chips. There is little to no accumulation of sediment on cards. There is no evidence of delamination. It is unknown if he regularly took his wallet in the water surfing with him which might result in heavier corrosion. This needs to be relatively scientific/ engineering/ forensic sounding and referenced. It also needs to tell a story and be kinda sexy with the potential murder/ missing person.
Also of note: I spoke to an OG Dominican guy about it and he said this sort of thing is common down there. Some one pays local sacarios to kill some one. They have a pretty girl drug a drink with some plant or root native to the island. The plant makes the person act erratically. They lead them to the beach and they are never seen again. Apparently they are knocked out, taken on a boat, stripped naked, weighted down, and dumped into shark-infested water so divers would not search the area anyway.
It is, however, very strange that his wallet was found with cash still inside.
A photographic study of potential corrosion of credit cards was carried out in order to discern the potential or rate for the corrosion or alteration of modern PVC credit cards in seawater. Photographic evidence was recorded at incremental times during a six week period while the credit cards were left confined in a mesh bag on the sea floor. The digital images were painstakingly studied for permanent markings related to the seawater exposure.
Over long periods of time, seawater is one of the most corrosive substances on earth. Much effort is expended to fight or mitigate the oxidative power of salt water. In this study we propose a photographic timeline of the degradation of credit cards left in seawater. We aim to give record in order to assist in timelines of corrosion for law enforcement.
Candice Oviatt produces some papers with good description of the Bay
The experiment was conducted at Allen’s Harbor North Kingstown. Allen’s Harbor is an inlet on Narragansett Bay. It is surrounded by both natural wetlands and manmade structures. The bottom composition is sandy mud with patches of eelgrass (Zostera marina). The bay is considered well mixed with more turbulent mixing occurring in the winter months.
Water temperature ranged from ____ at the surface to ____ at the seafloor.
Visibility was measured using a secchi disk at ____
Dissolved oxygen averaged ____mg/l
Narragansett bay is a highly productive waterway with chl A concentration during the testing period averaging ____ ug/ml
Salinity at the bottom was averaged at ____
The credit cards were placed in a mesh bag and weighted to the seafloor with rocks. The bag was secured with a rope to a dock with enough slack to allow the bag to remain on the seafloor during high tide. The bag sat at a depth of approximately 9 feet during low tide, 12 ft during high tide.
Materials and methods:
1:1 macro lense
4 plastic credit cards and 1 plastic membership card were procured and hole punched through to void them. The Cards were placed in a plastic mesh bag with small rocks to weigh the bag down. The Bag was lowered onto the bottom and secured to the warf with parachord. Digital photographs were taken in macro mode with a Nikon D5300 with 1:1 macro lense with white background.
The front and back of each card was photographed at time = 0,1day,2,3,4,5,1week, 2 w,3w,4w,5w,6w,7w. At week 7 the cards were taken back to the lab and studied under a microscope. The cards were then stored in plastic bag to replicate conditions of original sample cards
Results: The is no visual evidence of corrosion or delamination after 7 weeks under water.