{"id":170,"date":"2025-08-21T18:24:09","date_gmt":"2025-08-21T16:24:09","guid":{"rendered":"https:\/\/sites.unica.it\/superfici\/?page_id=170"},"modified":"2025-08-21T18:25:31","modified_gmt":"2025-08-21T16:25:31","slug":"corrosion-resistance-of-ni-p","status":"publish","type":"page","link":"https:\/\/sites.unica.it\/superfici\/corrosion-resistance-of-ni-p\/","title":{"rendered":"Corrosion resistance"},"content":{"rendered":"\n<p><strong>The corrosion resistance of electroless deposited nano-crystalline Ni-P alloys<\/strong><\/p>\n\n\n\n<p>Electroless Ni-P alloys produced as a coating on mild steel in a commercial autocatalytic hypophosphite- type plating bath were studied, with regard to their corrosion behaviour upon immersion in near neutral sulphate and chloride electrolytes. The anodic polarization curves of the alloys showed a current plateau at potentials E &lt; +0.2 V SCE confirming their high corrosion resistance. The dynamic cathodic polarization curves in deaerated solutions showed a pseudo Tafel behaviour with a slope of ca. -0.4 V SCE\/decade. Corrosion rates of ca. 0.5 \u2013 0.7 \u00b5A\/cm2 were found during prolonged immersion in near neutral solutions open to air. Potentiostatic polarization at selected potentials in the range of the current plateau (-0.1 V SCE, +0.1 V SCE) showed a steady decrease of the current density following a power law with exponent -0.5, thus a diffusion controlled process. These results show that the suppression of the anodic dissolution and the low corrosion rates of Ni-P alloys cannot be associated with the oxide-film passivity. Despite this fact, a kind of \u201clocalized corrosion\u201d appeared on mechanically polished and \u201cas plated\u201d electroless Ni-P deposits after prolonged potentiostatic polarization at potentials in the range of dissolution suppression.<\/p>\n\n\n\n<div class=\"wp-block-media-text is-stacked-on-mobile\" style=\"grid-template-columns:29% auto\"><figure class=\"wp-block-media-text__media\"><img loading=\"lazy\" decoding=\"async\" width=\"780\" height=\"718\" src=\"https:\/\/sites.unica.it\/superfici\/files\/2025\/08\/Cross_section_NIP.jpg\" alt=\"\" class=\"wp-image-171 size-full\" srcset=\"https:\/\/sites.unica.it\/superfici\/files\/2025\/08\/Cross_section_NIP.jpg 780w, https:\/\/sites.unica.it\/superfici\/files\/2025\/08\/Cross_section_NIP-300x276.jpg 300w, https:\/\/sites.unica.it\/superfici\/files\/2025\/08\/Cross_section_NIP-768x707.jpg 768w\" sizes=\"auto, (max-width: 780px) 100vw, 780px\" \/><\/figure><div class=\"wp-block-media-text__content\">\n<p>The composition of the NI-P coatings was determined by EDX as 18 &#8211; 19 at% phosphorus. Electrochemical experiments (potentiodynamic polarization curves, potentiostatic polarization) were performed in acidic and near neutral solutions both on &#8220;as plated&#8221; and on mechanically polished samples.\u00a0<\/p>\n\n\n\n<p>The anodic polarization curves showed a current plateau at potentials E &lt; +0.2 V SCE both in acidic and neutral solutions confirming the high corrosion resistance of the Ni-P alloys. Potetiostatic polarization in the potential range of the plateau showed a steady decrease of the current density following a power law with exponent -0.5, thus a diffusion controlled process.&nbsp;<\/p>\n<\/div><\/div>\n\n\n\n<p>These results show that the suppression of the anodic dissolution and the low corrosion rates of Ni-P alloys cannot be associated with the normal oxide-film passivity of nickel. The hypothesis of a diffusion control of the nickel dissolution through a phosphorus enriched film at the alloy surface will be tested with XPS surface analysis in a following paper.\u00a0<\/p>\n\n\n\n<p><strong>Publications<\/strong>: <\/p>\n\n\n\n<p>M. Crobu, Master Thesis at University of Cagliari (2007)<\/p>\n\n\n\n<p>M. Crobu, A. Scorciapino, B. Elsener, A. Rossi, The corrosion resistance of electroless deposited Ni-P alloys, Electrochimica Acta\u00a0<strong>53<\/strong>\u00a0(2008) 3364 &#8211; 3370\u00a0\u00a0<a href=\"http:\/\/dx.doi.org\/10.1016\/j.electacta.2007.11.071\" target=\"_blank\" rel=\"noreferrer noopener\">doi.org\/10.1016\/j.electacta.2007.11.071<\/a><\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>The corrosion resistance of electroless deposited nano-crystalline Ni-P alloys Electroless Ni-P alloys produced as a coating on mild steel in a commercial autocatalytic hypophosphite- type plating bath were studied, with regard to their corrosion behaviour upon [&hellip;]<\/p>\n","protected":false},"author":335,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-170","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/pages\/170","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/users\/335"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/comments?post=170"}],"version-history":[{"count":2,"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/pages\/170\/revisions"}],"predecessor-version":[{"id":174,"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/pages\/170\/revisions\/174"}],"wp:attachment":[{"href":"https:\/\/sites.unica.it\/superfici\/wp-json\/wp\/v2\/media?parent=170"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}