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Waterjetting & Surface-Tolerant Coatings: UHP on the Luís I Bridge in Porto, Portugal

From JPCL, October 2018

By Joao Azevedo, Sherwin-Williams Protective & Marine Coatings

The iconic Luís I Bridge, constructed in 1886, spans the River Douro between the cities of Porto and Vila Nova de Gaia in northern Portugal. In 2003, the bridge's upper deck was converted to carry the D Line of the Porto Metro light railway, necessitating an additional 22,000 square meters of extra structural steelwork requiring protection from corrosion. With the bridge protected since construction by a lead-based paint system, this article discusses the rationale behind employing ultra-high-pressure waterjetting and recoating the bridge with an ultra-high-solids, damp-surface-tolerant epoxy coating and reports on its success after 15 years in service....


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Comment from WAN MOHAMAD NOR WAN ABDUL RAHMAN, (10/29/2018, 1:36 AM)

Great article Joao. Its enlightened our knowledge about the usesage of UHP BLASTING .


Comment from Regis Doucette, (10/29/2018, 7:24 AM)

I enjoyed the presentation and wonder about the accidental covering up of active corrosion cells with your reference to imperfect protection around the bolt heads and connections. I understand your emphasis on the metrics of a small percentage of surface area, but structure critical areas are a small percentage in the same way that our eyes and ears are a small percentage of our own bodies' surface area. Bolts and connections are more important and may require a different approach to protective coatings such as the inclusion of a chemical treatment for corrosion mitigation.


Comment from Gordon Kuljian, (10/30/2018, 9:23 PM)

Great success story after 15 years. Maybe only one spot-touch up of the bridge before your 30 year report!


Comment from EDUARDO MARTINEZ, (10/31/2018, 6:17 AM)

Congratulations Joao and thank you very much to share. Respect to the waterjetting guns (6 units), could we consider a performance per lance between 3 and 5 m2 / hour? You could send me some more detail about the waterjetting equipment. You know I really like these "toys" ;-)


Comment from JOAO AZEVEDO, (10/31/2018, 6:57 AM)

Thank you everyone so kind to comment so far. @Regis Doucette, your comment well taken, and agree bolts and connections are critical. In the Luis I bridge a very small proportion of such critical areas showed imperfections, as good discipline was in place stripe coating it. Also routine touch up maintenance can early-spot such defects and correct it before rust creeping too much. This being said, other corrosion mitigation processes maybe used as you mentioned. @Eduardo Martinez, I'm well aware of your involvement with UHP, and you are a believer on its untap potential when adequate coating system is selected. At the time of this job, the rates that were mentioned worked well after experience curve went up. The state of art in UHP equipment evolved, so I believe you can get better intel on what is available now by contacting the major supplier of UHP equipment. Please note that rates can change a lot from project to project depending on coating system type and condition and access.


Comment from Francisco Giaquinto, (10/31/2018, 7:57 AM)

Parabéns João pelo esquema de pintura apresentado.A função do fundo amina é relevante na proteção dos ataques quimicos (névoa salina e poluíção promovida pela descarga de gases dos veículos) Já aqui no Brasil, fiz o tratamento de diversas pontes e o uso de tinta a base de zinco, pelo trabalho que a ponte recebe (vibração), um revestimento rígido de fundo, diminuí a vida útil do processo. Que fique claro também que o jateamento em ultra alta pressão é o caminho correto, quando se tem o histórico anterior da rugosidade promovida. Já que houve enclausuramento desta para a retira dos resíduos das tintas, o jateamento úmido com o abrasivo poderia ser utilizado. Sucesso.


Comment from JOAO AZEVEDO, (10/31/2018, 9:11 AM)

Obrigado Francisco. Na ponte Luis I o sistema de pintura utilizado foi especialmente adequado às necessidades, graças à capacidade de obter adesão muito superior à habitual sobre substrato hidrojateado, mesmo na presença de flor de ferrugem ou de humidade na sequência do hidrojato. As tintas de zinco normalmente não seriam compatíveis com o hidrojato, a não ser com grande condicionamento ambiental e rejateamento abrasivo da flor de ferrugem. O sistema de pintura na Luis I apresenta ainda uma flexibilidade superior à habitual (aprox 5% de alongamento de rutura - NACE RP394-2002), o que associado à adesão permite lidar sem problema com o desafio das vibrações numa estrutura como esta ponte.


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