海洋环境下钢材表面镀铝工艺的研究进展

Aluminizing Steel Surface for Providing Protection in Marine Environment:a Technological Review

钢材作为基础性结构材料被广泛应用于海洋工程领域,随着国家对海洋开发的支持力度不断加大,对应用于此环境下的钢材的需求也不断增加。但是,暴露于苛刻海洋环境下的钢材极易与周围的含氯、硫等介质发生反应而受到严重腐蚀,同时,潮汐、日照、溶解氧、微生物以及深海压力和热液带来的高温等环境条件也会加速钢材的腐蚀,严重影响海洋工程设施的服役安全、寿命以及可靠性。因此,对钢材进行表面处理提高其耐腐蚀性能成为研究热点,其中涂层制备技术是最常用的腐蚀控制方法。铝及铝合金在腐蚀环境及高温氧化环境下表面可以形成一层致密的氧化膜,是一种常用的耐腐蚀涂层材料,通过不同工艺在钢材表面制备的铝涂层已达到了长效的防腐蚀效果。目前,制备铝涂层的工艺主要有热浸镀法、电镀法、包埋渗铝法及热喷涂法等。热浸镀铝工艺因操作简单、成本低廉而被广泛应用于海洋平台、海洋码头、桥梁等海洋基础设施。电镀铝工艺制备的涂层厚度、组织、形貌可控,可以实现在微小零件上的精准沉积。新型绿色环保的离子液体体系的开发,在提高电镀效率和涂层质量的同时降低了对环境的污染。粉末包埋渗铝制备的涂层具有极高的抗高温氧化性能,被广泛应用于海洋油气开采工程。低温包埋渗铝工艺可避免传统渗铝工艺高温导致的钢材力学性能下降。此外,浆料渗铝以及气相渗铝等工艺的开发拓宽了渗铝工艺的应用领域。热喷涂工艺在海洋环境下应用最为广泛,所制备的铝涂层具有极高的耐腐蚀性能,其中火焰喷涂、电弧喷涂、冷喷涂等工艺能够实现新型防腐蚀铝涂层的设计与制备。本文针对海洋环境下应用的钢材,详细介绍了在其表面镀铝工艺的研究进展,包括热浸镀、电镀、包埋渗铝和热喷涂等,并对不同镀铝工艺在海洋环境下的应用及发展方向做了展望。

Steels have found extensive application in the field of marine engineering as one species of essential structural materials,and the continuous mounting support for marine resource utilization exaggerates the demand for steel products.The exposure of steel to harsh marine environment will easily lead to severe corrosion for the sake of the reaction between the steel and the surroun-ding chlorine-and sulfur-containing corrosive medium.Meanwhile,other minus circumstances,such as tides,sunlight,dissolved oxygen,microorganisms,abyssal sea pressure,and hydrothermal fluid-induced high temperature usually aggravate the corrosion of steels.These would seriously affect service safety,lifespan and reliability of marine engineering facilities.Therefore,aiming at improving the corrosion resistance of steel,researchers and engineers have paid much interest to the surface treatment techniques exemplified by coating preparation.Aluminum and its alloys can form a dense oxide film on the surface in corrosive and high-temperature oxidation environment.Aluminum coatings prepared on steel surfaces through different processes have been proved to have long-term corrosion protection efficacy.Currently,the common methods for preparing aluminum coatings include hot dipping,electroplating,embedding aluminizing,thermal spraying,etc.Owing to its simple operation and low cost,hot dip aluminizing process has been widely used in marine infrastructures,e.g.marine platforms,wharfs,bridges.Electroplating technique enjoys the advantage of controllable coating thickness,microstructure and morphology by moderate preparation conditions and adjustable process parameters,and has successfully achieved precise deposition of aluminum coatings on tiny parts.Furthermore,the newly emerging green and eco-friendly ionic liquid systems facilitate the improvement of electroplating efficiency and coating quality while reducing the pollution to environment.Aluminum coatings prepared by powder embedding process have excellent high-temperature oxidation resistance,which are widely used in marine oil and gas field.Moreover,low-temperature embedding aluminizing process can overcome the problem of high-temperature-induced mechanical properties deterioration with respect to traditional aluminizing process.In addition,the development of slurry aluminizing and vapor phase aluminizing has promoted the practical application of the embedding aluminizing process.Thermal spraying techniques,including flame spraying,arc spraying and cold spraying,are the most widely used aluminizing techniques which could obtain high-anti-corrosion protective surface against marine environment.This review provides a vivid description of the research progress with respect to aluminizing process used to prepare aluminum coatings on surface of steels which serve under the marine environment,including hot dipping,electroplating,embedding aluminizing and thermal spraying.It also gives a brief prospective discussion over the potential application and development tendency of these various aluminizing techniques.