Preparation And Characterization Of Flame Sprayed Cu-coated Polyethylene Composite Coatings

With the development of the marine industry,corrosion and biofouling problems have drawn worldwide attentions.Thermal spraying technology with low cost efficiency,can choose coating material widely,and convenient for field operation,such advantages making it become a kind of the most promising surface coatings technology.The polymer is widely used in many field due to the lightness,easy forming,low cost and chemical resistance etc..Studies have shown that the thermal spray polymer coatings have excellent corrosion resistance and copper containing coatings have good antifouling properties.Therefore,the combination of polymers and the biocides to study the new antifouling and anti-corrosion coatings to reduce the pollution of marine engineering materials is an urgent need to solve the scientific problems.Therefore,it is necessary to develop the both antifouling and anti-corrosion composite coatings.In this paper,the high density polyethylene(HDPE)-Cucore-shell structure particles were used as feedstock for flame spraying.And it was prepared by electroless copper plating on the surface of HDPE particles.And the pure HDPE coatings,HDPE-Cu composite coatings and pure Cu coatings were successfully deposited on the Q235 mild steel by flame spraying.The phase composition,morphology,thermal properties and surface characteristics of the coatings were characterized.And the antifouling properties,corrosion resistance properties and anti-ageing properties of coatings were assessed.Results showed that the HDPE-Cu composite particles presented the core-shell structure using the electroless plating technique.Copper shells with a thicknessof ~1?m surrounding individual HDPE particles were obtained.The fluidity of composite particles better than the pure HDPE particles due to the metallization of the polymer surface.It could be improve the film-forming efficiency of the HDPE particles.The dense structures havebeen achieved,and no marked flaws for instance microcracks or poresare seen from the coatings.The content of copper on the surface and in the innerof the composite coatingswere 35.11 ± 2.63 vol.% and 9.57±1.28 vol.%.XRD detection suggests noextra peaks are seen except those for copper and HDPE,indicating negligibleoxidation or other undesirable chemical changes during electroless plating and flame spraying process.Cu shell can effectively protect HDPE core and decrease decomposition temperature of polymer during the heating process.The assessment to the antifouling properties of the HDPE-Cu coatingsreveals significantly prohibited attachment of Bacillus sp.bacteriaon their surfaces.It is noted that after 3 days exposure in the bacteria containingASW,the HDPE coatings show clear colonization of the bacteria.In contrast,the Cu-containing coatings and the coppercoatings show the attachment of few bacteria.Antimicrobial results showed that the antimicrobial rates of HDPE-Cu and Cu coatings are more than 99%,nevertheless the HDPE coatings is below 50%.The copper ions release results showed that the concentration of copper ions is 0.003 ppm it canrepel recruitment of Bacillus sp.and E.coli..In the first 3 days,the release rate ofcopper ions is relative high.With further elongated incubation of the coatings,release rate of copper ions decreases and reaches a relatively stablevalue.Image analysesfrom the surface and the cross-section of the coatings incubated in thesolution for 21 days reveal that the content of copperon the surface and the interior of the HDPE-Cu coatings is 10.91±3.17 vol.% and 9.15 ±1.17 vol.%,which indicates that copperwithin the composite coatings do not easily dissolved into the solutionin short time due to the protection of the inert polymeric matrix.Continuous release in low-dose of copper ions confers long-term antifouling capability on the coatings.Neutralsalt spray results showed that thesurface and the cross-section of the HDPE-based coatings still exhibit intactstate after 14 days exposure to the corrosive media.7 days exposure of the copper coatingsresults in full coverage of the corrosion products,suggesting favorable anti-corrosion performances.Study found that corrosion potential and current of HDPE-Cu composite coatings are-0.100 V and1.304×10-7A/cm2,respectively.And the Rct charge transfer resistance is 4.09×105?·cm~2,the corrosion reaction resistance increases,the corrosion rate slows down.HDPE-Cu composite coatings wereaged in xenon lamp ageing testing chamberresults showed that there is no chemical composition variationin the HDPE-Cu coatings.Cracks were found on thesurfaces of the HDPE coatings,while the HDPE-Cu coatingsshow almost intact surface morphology after ageing 21 days.The Cu shellsenhanced the decomposition temperature and thermal stabilityof HDPE in the composite coatings.Therefore,Cu can obviously improve the anti-ageing properties of the HDPE polymer.