Microbiologically Influenced Corrosion is the accelerated corrosion of a metal surface due to the presence of a biofilm. Metal corrosion typically result in formation and accumulation of corrosion products in the form of tubercles and rusticles. Rusticles are a corrosion product with an icicle-like morphology only found on deep water iron structures (>1000 m below sea level). A similar type of corrosion products with slightly different morphology are tubercles, commonly found on iron structures throughout the water column and in drinking water distribution systems. They are thought to be formed by a combination of iron oxidising/reducing and sulphate reducing microorganisms and the chelating properties of both the iron and the extracellular polymeric substances produced by said microorganisms. Both rusticles and tubercles are mainly composed of goethite and lepidocrocite (α-FeOOH and γ-FeOOH, respectively). MIC diagnosis and assessment typically involve isolation of DNA from corrosion products for identification of microbial consortium involved in metal deterioration. However, the extraction of DNA from rusticles and tubercles is problematic due to the co-extraction of iron and the subsequent interference with downstream processing. The fact that DNA adsorbs onto iron oxides constitutes a major problem for MIC studies and the DNA based techniques commonly used to diagnose, detect or monitor it. High concentrations of iron oxides inhibit the DNA extraction by interacting with its polyphosphate backbone, backbone that is also used to bind the DNA to the silica spin columns in popular extraction kits like the PowerSoil kit (Qiagen). Here we present a protocol to separate the adsorbed DNA and cells from the corrosion products and then the extracellular DNA from the microorganisms to reduce the bias from external sources of DNA.