Once installed at the seabed, subsea rigid pipes in Carbon steel (CS), Low Alloys Steels (LAS) or in Corrosion Resistant Alloys (CRAs) can be wet stored for various durations. During this idle period, the lines can be filled with natural seawater generally treated with different types of chemicals, to mitigate localized corrosion initiation of stainless steel or the general corrosion of carbon steel. The chemicals are usually oxygen scavengers combined with or without biocides and corrosion inhibitor. Field experiences show that satisfying efficiency is obtained with some chemical’s combination. However, only few data are available in the literature to quantify separately the actual benefit of these chemicals and their combination. The needs to investigate sustainable alternative chemicals for these wet storage operations are also anticipated. In order to quantify the individual and synergistic effects of the selected chemicals, API 5L X65 carbon steel and UNS S31603 stainless steel were exposed for one year in seawater treated by different available combinations of oxygen scavenger, biocides, and corrosion inhibitors. Environmental-friendly chemicals have also been assessed as possible alternatives to conventional biocides. The corrosion rate of carbon steel coupons immersed in specific exposure cells, that simulate the confined exposure conditions during the wet storage, have then been determined by weight loss measurements after 3 weeks, 2, 6, and 12 months. The impact of the treatments on the corrosion rate and the bacterial activity have also been studied by Dissolved Oxygen Content (DOC) and Open Circuit Potential (OCP) monitoring, Electric Resistance (ER) measurements, and bacterial analysis. The current investigation shows that low DOC levels have been achieved which inhibited the so-called “biofilm ennoblement” of stainless steel. Thus, no corrosion occurred for UNS S31603. Such results are also applicable to most CRAs under similar exposure environment. The synergic effects of oxygen scavenger, biocides and corrosion inhibitor on the corrosion rate of carbon steel are also discussed.

Once installed at the seabed, subsea rigid pipes in Carbon steel (CS), Low Alloys Steels (LAS) or in Corrosion Resistant Alloys (CRAs) can be wet stored for various durations. During this idle period, the lines can be filled with natural seawater generally treated with different types of chemicals, to mitigate localized corrosion initiation of stainless steel or the general corrosion of carbon steel. The chemicals are usually oxygen scavengers combined with or without biocides and corrosion inhibitor. Field experiences show that satisfying efficiency is obtained with some chemical’s combination. However, only few data are available in the literature to quantify separately the actual benefit of these chemicals and their combination. The needs to investigate sustainable alternative chemicals for these wet storage operations are also anticipated. In order to quantify the individual and synergistic effects of the selected chemicals, API 5L X65 carbon steel and UNS S31603 stainless steel were exposed for one year in seawater treated by different available combinations of oxygen scavenger, biocides, and corrosion inhibitors. Environmental-friendly chemicals have also been assessed as possible alternatives to conventional biocides. The corrosion rate of carbon steel coupons immersed in specific exposure cells, that simulate the confined exposure conditions during the wet storage, have then been determined by weight loss measurements after 3 weeks, 2, 6, and 12 months. The impact of the treatments on the corrosion rate and the bacterial activity have also been studied by Dissolved Oxygen Content (DOC) and Open Circuit Potential (OCP) monitoring, Electric Resistance (ER) measurements, and bacterial analysis. The current investigation shows that low DOC levels have been achieved which inhibited the so-called “biofilm ennoblement” of stainless steel. Thus, no corrosion occurred for UNS S31603. Such results are also applicable to most CRAs under similar exposure environment. The synergic effects of oxygen scavenger, biocides and corrosion inhibitor on the corrosion rate of carbon steel are also discussed. 

The use of organic coatings in conjunction with cathodic protection (CP) for buried structures is the usual method for protecting steel against corrosion. When the organic coating loses its protective ability, regardless of the reason, the CP becomes the active protection, leading to a specific local environment. This environment can be characterized by high alkalinity, which can be detrimental for the coated structure, either by weakening the steel–coating interface or by the chemical aging of the coating. Thus, the coating must be compatible with CP and able to sustain aging under an alkaline environment. In this study, the susceptibility to alkaline aging and its consequences in regards to coating performance have been investigated for two commercial coatings used for buried structures—fusion bonded epoxy (FBE) and liquid epoxy (LE)—in free membrane and coated steel configurations. The results showed a clear impact of alkaline aging on the studied LE, leading to a significant reduction in coating resistance and ultimately, failure of the steel–coating interface, whereas the studied FBE remained stable. The presented results relate to a precise formulation of LE and FBE; however, the proposed chemical method appears to be relevant and shows the necessity of considering such specific aging results for coating specifications and improvements.

In France, deep geological disposal is considered for the storage of high and intermediate-level long-lived radioactive wastes. For aluminium, the possibility to encapsulate the wastes in a cement-based matrix is studied. However, cement being an alkaline environment, aluminium can lose its passivity, starts to corrode leading to hydrogen evolution in the infrastructures and generate a possible explosive hazard after decades of storage if hydrogen can accumulate somewhere in the facility. It is therefore necessary to study the corrosion behaviour of aluminium in the different cements considered for the encapsulation to estimate the possible amount of hydrogen that could be generated through corrosion and design the cement capsules accordingly. This work mainly focused on the reaction occurring at the aluminium-cement interface. Raman spectroscopy did not highlight significant differences in the nature of the corrosion products forming at the cement/aluminium interface, leading to the conclusion that it is not the chemistry of the cement that is the key factor controlling the corrosion rate but rather the physical properties of the cement matrix. 

Anticorrosive coatings are widely used to protect steel against corrosion. Different standards exist to access the corrosion performance of anticorrosive paints. Among them, the so-called neutral salt spray test (NSST-ISO 9227) or cycling corrosion tests ISO 12944-6, ISO 12944-9, NACE TM0304, or NACE TM0404 can be named. It is well-known that some accelerated corrosion tests are not fully representative of the field exposure results. However, a lack in the literature exists correlating accelerated tests to field exposure, especially when long-term durations are considered. In this study, 11 different organic coatings have been investigated in terms of coating resistance to corrosion creep in two types of field exposure sites, namely a stationary site and an operating ship, and their performance was compared to two accelerated tests (ISO 12944-9 and modified ASTM D5894 standard). The results showed differences in the sites’ corrosivity and the coating systems’ performance as a function of the exposure sites. A lack of correlation exists between the ISO 12944-9 standard and the stationary site, due to the latter’s high corrosivity, while, to the contrary, a satisfying correlation with the operating ship was demonstrated; whereas, the modified ASTM D5894 standard showed a satisfying correlation with both types of sites.

Carbon steel samples covered with initially crack-free zinc-nickel coatings were polarized with a small anodic overpotential in moderately alkaline NaCl solution. Along with zinc dissolution, the coatings developed a mud-crack pattern due to tensile stress release, allowing the electrolyte to access the underlying steel surface. Simonkolleite grew on both the zinc-nickel coating and the steel substrate. The resulting current density, that was first strongly anodic, switched to small cathodic values when the coating surface was almost fully covered by a compact simonkolleite layer. 

It is well known that the surface state (cleanliness, composition) of galvanized steel prior to the application of an organic coating is an important parameter. The surface state will affect the adhesion properties of the complete system and therefore will also impact its corrosion resistance and its tendency to blistering. Before the application of a pretreatment layer, galvanized steel strips are normally alkaline cleaned. This step is known to remove the native oxide film formed on hot dip galvanized steel after processing and appears as one of the most important steps to study the impact of the surface properties on the performance of painted systems. This study focused on making use of the cleaning step to input a variability on the surface composition (mainly surface concentration of aluminum) and evaluate its consequence(s) on the performance of a complete paint system. The results showed that, a variability in terms of surface aluminum concentration could be achieved by the cleaning step and that signs of performance improvement in terms of adhesion and tendency to blistering were spotted with a low content of aluminum at the surface.

The constant change in coating technology and environmental regulations has led to the development of low-solvent to solvent-free organic coatings, such as powder and high-solid coatings. These two technologies are well developed, but are still not the preferred choice when considering anticorrosive coating for marine and offshore applications. This mostly arise from a lack of perspective in their long-term behavior and from the difficulty in their applications. This review's principal aim is to describe powder and high-solid technologies from their formulation and application to their use in marine and offshore applications while recalling and giving key notions needed when the field of anticorrosive coatings is considered. First, the requirement for coatings to be called anticorrosive will be given alongside with their protection and failure mechanisms. The formulation and application for high-solid and powder coatings will be exposed followed by the description of the type of coating chemistry used in harsh environment. Finally, high-solid and powder coatings behavior in these types of environment will be discussed. © 2020 by the authors.

Several studies sponsored by the French Naval Authorities have been conducted during the last 10 years aiming to develop more reliable testing conditions than the conventional neutral salt spray test that should not be used for prediction of material performance. A satisfying correlation to atmospheric field exposure on a ship in service was observed using a 6 months cyclic test from the automotive industry (e.g., Volvo STD23-0014) with a deviation inferior to 25% and an acceleration factor of 4. The possibility to shorten the test duration with a target of 3 months without losing correlation to field exposures is investigated in the present study. A design of experiment is used to study key parameters such as NaCl concentration, the mode of salt application and its frequency as well as the temperature. Ten different marine paint systems used for shipbuilding have been selected. The results indicate an enhancement of the aggressiveness of the test when doubling the salt concentration from 1 to 2 wt%, increasing the number of salt spray per week (from 2 to 3), and the temperature from 35 to 45 °C. The data are compared to marine field exposures in tropical and temperate climates. The most reliable testing conditions to field exposure in marine sites of severity from low C5M to CX on steel include cyclic corrosion tests using 2 wt% of NaCl.