Three corrosion problems solved
Methods
Three corrosion problems solved
Keywords Corrosion resistant, Denso, Linings, Steel
Global Environmental Services of Knowesthorpe Lane, Leeds, UK, are a waste management company and operate a fleet of tankers to carry waste materials to approved disposal sites. Occasionally solvents, acids and effluents that are carried by Global's tankers can attack the linings and in consequence these are regularly checked by spark testing for pinholes or more serious defects.
Global Environmental Services tankers are serviced and maintained at the Ledston Luck, Leeds,premises of Vallely Engineering Ltd, who are also tanker manufacturers. They work in conjunction with Repair, Protection and Maintenance Ltd, the corrosion engineers of Pontefract, who are direct suppliers to Global for the specialist work of testing the integrity of the tanker lining. In most cases it will be found that there are only a few pinholes in the lining, which are then touched in with a compatible material.
More recently the spark testing on one Global tanker revealed that the lining had suffered attack from a particularly aggressive cocktail of effluents. RPM shot blasted localised areas of damaged coating back to bare metal and then spray applied 2 ram of Winn &Coales Archco-Rigidon Tankerline 403D coating, followed by a top coat used to give additional longevity and resistance to certain cargoes such as hydrofluoric acid. Archco-Rigidon Tankerline is formulated from a glass flake filled vinyl ester resin (Plate 2).
RPM's procedure for all its tanker customers is to thickness check the tanker barrel randomly at approximately five readings per m2; record the highest, lowest and average readings and note any areas of concern. All the coated areas of the road tanker barrel are spark tested by section, including pipe and flange connections, with particular attention to areas more susceptible to damage, such as manway lids and baffle plate edges. Any sparking to the substrate is chalk marked and repaired as necessary. A verbal report is given to the customer if anything more than minor touch up repairs are required.
A key feature of Peter Pan's Adventure Island on the Western Esplanade at Southend-on-Sea is the log flume ride. It is supported by zinc coated steel columns, with the base of the columns standing in a shallow "lake" filled with fresh water, treated to prevent bacterial and algal growth.
As part of its ongoing safety programme, during routine maintenance by Stockvale Ltd, the owners and operators, the lake was drained to reveal that the zinc coating was failing and the bases of the columns were beginning to corrode.
Stockvale Ltd contacted anti-corrosion coatings specialists Winn & Coales (Denso) Ltd, who recommended their new Protal ST Epoxy Mastic to give long life protection.
The columns were scraped and cleaned with powered wire brushes to remove all loosely adhering corrosion products by Stockvale's labour force before application of two coats of the Protal ST coating.
This surface tolerant coating can be brush or spray applied to deliver long-term protection in a wide range of corrosive environments. Its exceptional adhesion properties are designed for surfaces which have been hydrojetted or power tool prepared. Other benefits claimed for the environmentally responsible coating include:exceptional wetting and deep penetration properties; high mechanical saving due to fewer coats; cures at temperatures as low as 10°C.
Plate 2 The Global tanker relined with Archco-Rigidon Tankerline
Anglian Water is making a£30m investment in a new wastewater treatment project to handle the whole of Grimsby's domestic sewage, plus treatment of local industrial waste water(Plate 3).
Plate 3 Applying Densoclad 70 to a 1,000mm pipe at Anglian Water's new Grimsby wastewater treatment plant
As part of the overall project, one of Anglian Water's contractors, Clugston Constructions, is currently installing two 400 metre piperuns of 1,000mm ductile iron pipes to link the existing terminal pumping station with the new treatment plant.
The spigot and socket pipes with anchor joints are to be protected with Winn & Coales' Denso Profiling Mastic and Densoclad 70 tape to a P2 specification.
Densoclad 70 is a robust heavy duty tape specifically designed for the protection of medium to large diameter pipe and welded joints. The tough pv backing combined with a polymer bitumen adhesive ensures complete protection against hostile environments,including immersed conditions, as well as resistance to damage by impact during backfill of the pipe trench.
