Study On The Spatial Distribution Characteristics Of Initial Corrosion Rates Of Typical Steels In The Yellow Sea And East China Sea

With the development of the marine industry,we gradually moved from the offshore to the open ocean.However,the corrosion of marine steel in the marine environment cannot be ignored in the process of going to the ocean.Recently,researches on the corrosion of seawater are mainly focused on the coastal and indoors laboratories,and it means the lack understanding of how the corrosion rate of steel in the actual sea area is spatially distributed,whether its distribution in the ocean exhibits a spatial autocorrelation,and whether the data quality meet the requirements of spatial interpolation.On the basis of such a background,this article selects the Yellow Sea and the East China Sea as the research areas.Five kinds of steels,Q235 steel,45 # steel,X80 pipeline steel,EH36 steel,and 316 L stainless steel,were tested on the sea in the research areas.The initial corrosion rate obtained from the kinetic potential polarization curve was used as a research object.The spatial autocorrelation of the initial corrosion rates of the five steels in the spatial distribution was explored by geostatistical methods,and their semivariograms were calculated to draw different steels.The spatial interpolation map of the corrosion rate distribution and the data of different steels are combined to give a comprehensive corrosion risk distribution map of the research sea area.The main conclusions of this article are as follows:(1)Most of the distribution of the typical steel's initial corrosion rate in the Yellow Sea and the East China Sea have spatial autocorrelation,and this shows that it is affected by structural factors more than randomness factor in ocean.(2)In the Yellow Sea,Q235 steel,45# steel,X80 pipeline steel,EH36 steel,and316 L stainless steel are spatially correlated in the spatial distribution of the initial corrosion rate in August;Three kinds of steels,45 # steel,EH36 steel,and 316 L stainless steel,have spatial autocorrelation in the spatial distribution of the initial corrosion rates in December.Most typical steels have strong spatial autocorrelation in the Yellow Sea.The spatial autocorrelation range is about 60 km ? 400 km.(3)In the East China Sea,three kinds of steels,Q235 steel,EH36 steel,and 316 L stainless steel,have spatial autocorrelation in the spatial distribution of the initial corrosion rates in May.In September,two kinds of steels,X80 pipeline steel and EH36 steel,have spatial autocorrelation in the spatial distribution of the initial corrosion rates.About half of the steels,which have spatial autocorrelation,have strong spatial autocorrelation.The spatial autocorrelation range of steel is about100?200km in May and more than 500 km in September.(4)The spatial interpolation map showed that,in research area of the Yellow Sea,the initial corrosion rate distribution of Q235 steel,45# steel,X80 pipeline steel and EH36 steel showed a lower distribution pattern in the south than in the north in August.In December,the corrosion distribution of 45# steel and EH36 steel was similar,which show a trend of low in the middle and high in the surroundings.The distribution of 316 L steel showed higher in the middle,lower in the north and south in August,and a trend of a lower in the south and higher in the north in December.(5)The spatial interpolation map showed that,in research area of the East China Sea,the initial corrosion rate distribution of Q235 steel and EH36 steel in May showed a trend of higher along the coast and lower in the southeast,and the distribution of 316 L steel showed a trend of higher in the middle and lower near the north and south.In September,the corrosion distribution of X80 steel and EH36 steel showed a trend of lower in the south and lower in the north.(6)The distribution map of comprehensive indicator of corrosion risk showed that the central of the Yellow Sea and the coast of Jiangsu are high-risk areas of corrosion in August and December.In the East China Sea Research Area,there is no high-risk area for corrosion in September,and the southern part is a high-risk area for corrosion.