Corrosion analysis of ferrous hull plate samples from wrecks in Scapa Flow

Date April 2013 - January 2014

Event ID 1172946

Category Project

Type Project

Permalink http://canmore.org.uk/event/1172946

The Ministry of Defence (Salvage and Marine Operations) commissioned a project to recover and analyse a number of ferrous plate samples from shipwrecks in Scapa Flow with a view to establishing corrosion rates on the wrecks. The work sought to attain a better understanding of the safety and environmental implications of wreck decay but was also considered to possibly be of archaeological and historic value. Determining the corrosion rates of historically significant wrecks may, for example, prove useful in informing the future management strategies for such sites.

Seven samples were recovered by commercial divers from the sites of SS Prudentia, Sms Karlsruhe (under scheduled monument consent), HMS Royal Oak and HMS Vanguard. The samples were analysed in laboratory conditions and the data generated was used to determine corrosion rates based on the Weins Number Methodology.

The work was undertaken by S&MO (MoD) and Intertek.

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Related Event(s)

Event	Type	Subtype	Notes	Date
1173785	DOCUMENTARY REFERENCE	SPECIALIST REPORT	Corrosion analysis based on the Weins Number Methodology was undertaken on two samples of steel from HMS Royal Oak. The samples were identified as ‘Royal Oak – Torpedo bulge Depth 8m collected 26/4/1’ and ‘HMS Royal Oak Sample 2 26/4/13/ 24m’. Laboratory analysis by Intertek indicates that the sample from the torpedo bulge had a measured plate thickness of 11-12.4mm with concretion on both sides of the plate. Iron contents of the concretion of this sample was measured at 21.4% by weight. Sample 2 had two different thicknesses of steel as it had a ‘T’ formation with a thicker section and rivet holes. Iron contents of this sample was measured at 41% by weight. The average corrosion rate from sinking in 1939 to recovery of the two samples in 2013, as calculated from concretion data, was measured at 0.0055-0.0127 mm/year. [...]	January 2014
1173585	DOCUMENTARY REFERENCE	SPECIALIST REPORT	Corrosion analysis based on the Weins Number Methodology was undertaken on one sample from HMS Vanguard probably collected from the debris field around the wreck. The sample identified as ‘HMS Vanguard Sample 3 27/4/13 32m’ comprised two samples in a crate. Both appeared to be heavily concreted, deformed angle sections. Laboratory analysis by Intertek involved detailed examination of one of these samples. Concretion made up the vast majority of the sample mass; only two small, jagged sections of corroded metal plate were recovered with a maximum measured plate thickness of 4.5mm. Iron contents of the sample was measured at 45% by weight. The average corrosion rate from sinking in 1917 to recovery of the sample in 2013, as calculated from concretion data, was measured at 0.0275 mm/year. [...]	January 2014
1173505	DOCUMENTARY REFERENCE	SPECIALIST REPORT	Corrosion analysis based on the Weins Number Methodology was undertaken on one sample from SS Prudentia. The sample was identified as ‘Prudentia 2/5/13 26m Forward Stores hatch’. Laboratory analysis by Intertek indicates that the steel plate sample had a measured plate thickness of 0-9.3mm, with concretion on both sides of the plate. There were two obvious rivet holes through the plate prior to concretion removal. Iron contents of the sample was measured at 35.4% by weight. The plate was heavily pitted and had thinned and perforated producing a ragged edge. The thickest regions were around the rivet holes. The average corrosion rate from sinking in 1916 to recovery of the sample in 2013, as calculated from concretion data, was measured at 0.0169 mm/year. [...]	January 2014

Corrosion analysis of ferrous hull plate samples from wrecks in Scapa Flow

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