(EnergyAsia, October 25 2011, Tuesday) — MTM Metalizing, a world leading US-based thermal spray coating provider, said it will be carrying out thermal spray aluminium (TSA) coating works for China Power Station in Hong Kong on a sub-contract awarded by Leighton Contractors (Asia).
MTM Metalizing will provide TSA coating on three pipelines and fittings to replace three 15-year old pipelines that form the main feed lines to three of the turbines running the generators at the power plant. The initial phase of the project is expected to last from August 2011 until next February.
Stress corrosion cracking is difficult to detect but is well known to occur when stainless steel is in the presence of chlorides (e.g. from seawater) – and this is not visible to the naked eye or easily detectable with common non-destructive testing (NDT) methods.
Metal parts with severe stress corrosion cracking can appear bright and shiny, while being filled with microscopic cracks. Corrosion cracking often progresses rapidly, and is more common among alloys than pure metals.
Bill Jordan, general manager of MTM Metalizing, said:
“The TSA coating is being applied onto the stainless steel pipeline to prevent stress corrosion cracking (SCC) which can be prevalent on stainless steel pipelines. As the line being coated is a gas pipeline, failure could potentially be catastrophic.”
MTM Metalizing will apply TSA coating on three sets of stainless steel pipes and fittings.
According to Mr Jordan, the standard six-metre long pipe and fittings will be coated in Singapore and then shipped to Hong Kong where they will be fabricated to the desired configuration. After fabrication and final installation and testing, the weld joints will be TSA coated on site in Hong Kong.
For this project, a challenge arose in the form of the coating thickness measurement as the stainless steel in non magnetic, and both the stainless steel metal and the aluminium coating are conductive. This means using a standard coating thickness gauge to measure the coating thickness is not possible.
Mr Jordan said that one of the few ways to measure the coating thickness is to use a comparator plate.
“As we are coating the pipes for this project, which is a more complicated geometry than plate, we had to further verify and test by coating 8” diameter steel sample pipes and then measure those pipes after TSA coating to ensure the sprayers could replicate the same speed and rhythm in coating, i.e. coat to the required thickness. All sprayers passed this test witnessed by the customer,” he said.
“The primary advantages of a TSA coating are the long life durability, cost-competitiveness compared to ‘high-quality’ paint schemes, enhanced protection courtesy of the oxide layers formed by the TSA coating, cathodic and surface protection, excellent resistance to marine environments, low-life cycle cost, minimal maintenance and exceptional competitiveness when compared to the options of changing base materials.”
The three sets of pipes and fittings in Singapore have been coated and witnessed by the QC representative from the customer, who commented “It was great working with professionals” after the coating was completed.
MTM Metalizing, a world leader in thermal spray coating applications, specialises in manual twin wire electric arc and manual flame spray application. Its metalizing machines are manufactured by IMC in New Jersey, US and registered with the US Patent Office and the Paris Convention of Countries. The IMC-patented technology used by MTM Metalizing is the current state of the art system for corrosion prevention.
In Singapore, the company has provided thermal spray coating services for an ExxonMobil plant on Jurong Island, The Sail at Marina Bay and Bluewater Energy Services at Sembawang Shipyard.