Hardide has proven resistant to sulphide stress cracking and stress corrosion in hydrogen sulphide (H2S) environments

Hardide, the unique tungsten carbide coating, has proven resistant to sulphide stress cracking and stress corrosion in hydrogen sulphide (H2S) environments in independent NACE TM0177 tests performed by Bodycote Materials Testing. Bodycote tested an uncoated control sample of 17-4PH stainless steel and a series of Hardide-coated 17-4PH stainless steel, Inconel 625 and 316l stainless steel samples. All were deformed to apply strain ranging from 1500 to 3000 microstrain and kept for 30 days in the standard test solution containing 5% sodium chloride and 0.5% acetic acid, and saturated with 99.5% purity H2S.

The uncoated control sample cracked across the full 20mm width and showed pitting on the stressed surface.

None of the NACE approved coated samples showed cracking, coating degradation including blistering or delamination when analysed by microscopy, dye penetrant, ultrasonic and metallographic examinations.

Dr Yuri Zhuk, Technical Director of Hardide Coatings Limited, the company which developed Hardide, commented: 'These results demonstrate that Hardide will protect components from sulphide stress cracking even under significant strain and deformation'.

'H2S is very aggressive against steel and causes severe embrittlement and cracking'.

'This can have potentially hazardous results when safety valves or pipelines are affected, as well as cause significant maintenance and downtime costs'.

'Effective protection against H2S stress cracking is particularly important in situations where the components are mechanically loaded'.

'In economic-driven industries such as oil and gas, mining and petrochemicals, the requirement to handle aggressive media including H2S over a wide range of tensile stress, temperature and pressure is ever increasing'.

'As a result, the development of resistant materials such as Hardide is assuming high importance in providing safe and cost effective solutions,' concluded Dr Zhuk.

Hardide combines hardness, toughness, low friction and chemical resistance.

It is a homogeneous, binder-free tungsten carbide produced by low temperature chemical vapour deposition (CVD).

It can be applied to steel, alloys and other materials with a coating thickness ranging from 5 to 100 microns, and can coat internal surfaces and complex shapes.

Hardide is in use in drilling, downhole and valve applications in the oil and gas industry around the world.

It is also in use in the aerospace, power, chemical and food manufacturing industries.

The coating received approval from BAE Systems for use on components for the Eurofighter Typhoon earlier this year.

The coating is the result of 25 years of research and development.

A commercial coatings facility has been operational in Bicester, Oxfordshire since 2003 and the company's first international coatings plant will open in October 2006, in Houston, Texas.