About: http://webisa.webdatacommons.org/295546467

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Agree with ventad, the cause of sludge is oxidation, sludge is a mixture but mostly rust corroding from the system, (a very small amount comes from galvanic action) and can only occur when oxygen is present in the water.
http://www.w3.org/ns/prov#wasQuotedFrom	pcadvisor.co.uk