DENSO P1 SYSTEM^™ BOLT CORROSION TESTING REPORT

BACKGROUND

In the water industry it is common to install pipeline fittings with either plain stainless-steel bolts or differing steel grade bolts protected by a factory coating. While the fitting itself is often protected from corrosion by more robust means, the bolts are often overlooked and left without sufficient corrosion protection. Any corrosion protection provided by factory coatings can be easily damaged in transit or during installation. The unprotected bolts provide an opportunity for destructive corrosion to occur, leading to bolt failure and in turn, potentially dangerous and costly incidents. To combat this issue, Denso recommends the Denso P1 System^™, designed for the protection of ferrous pipes, joints and fittings within the water industry in accordance with ‘Civil Engineering Specification for the Water Industry – 8th Edition’. It comprises a coat of Denso Paste^™ followed by the use of Denso^™ Profiling Mastic to fill any voids over joints to form a smooth profile. The system is completed by the application of a double layer of Denso Tape^™.

TESTING

In this investigation, bolts were installed onto a small-scale version of a common water pipeline fitting and Salt Spray testing was performed to replicate a highly corrosive environment. Three different bolt types were tested to represent the commonly used bolt materials and factory coatings. Half of the samples were protected with the Denso P1 system^™, and the other half were left unprotected, as received from the supplier.

Note: Salt spray exposure was performed based on ASTM G85-19 (Annex A5, X6) for 2000h.

RESULTS & CONCLUSIONS

The results demonstrate the severity of corrosion that can occur on bolts which are not protected by the Denso P1 System^™. All bolt types showed significant corrosion when unprotected however all the samples protected with the Denso P1 System^™ did not display any signs of corrosion.