The corrosion control of WC-Co type hardmetals is steadily gaining momentum for novel crucial applications in the Oil & Gas and food industries. The corrosion rate of the Co-based binder, and the extent to which coupling to WC speeds it up, are strongly influenced by alloying. In this paper, we investigate the impact of Cr on the corrosion-product film formation of Co- and CoNi based hardmetal binders in acidic, neutral and alkaline aqueous solutions. We centred our study on the role of Cr in driving the distribution of oxidized Co and Ni at the micrometre scale, thanks to synchrotron-based soft-X ray microspectroscopy. We have investigated morphochemical distributions for the following grades: Co₉₆Cr₄, Co₄₈Ni₄₈Cr₄, Co₅₀Cr₅₀. Chemical-state mapping has been complemented by electrochemical measurements and metallographic observations. Amounts of Cr and Ni of ca. 50% notably increase the corrosion resistance in all ambients, with a stronger beneficial effect of the former element. 4% addition of Cr results in slight positive effects, with the exception of the CoNi system in alkaline ambient, that, together with Co₅₀Cr₅₀, outperforms the other grades. In all investigated alloy-ambient combinations, a continuous oxidized metal film grows, onto which micrometric island form of shape and dimensions that depend on the specific grade and aggressive conditions. Quantitative descriptors of chemical-state maps and their theoretical interpretation in terms of electrochemical phase-formation by oxy-hydroxide precipitation, allow to correlate the island patterns with the degree of pseudopassivation.

WC-Co型硬质合金的腐蚀控制在石油和天然气及食品工业中的重要新应用中正稳步增长。钴会严重影响钴基粘合剂的腐蚀速率以及与WC结合的速度。在本文中，我们研究了Cr对酸性，中性和碱性水溶液中Co-和Co Ni基硬质合金粘结剂腐蚀产物膜形成的影响。由于基于同步加速器的软X射线光谱技术，我们集中研究了Cr在微米级驱动氧化的Co和Ni分布中的作用。我们研究了以下等级的形态化学分布：Co ₉₆ Cr ₄，Co ₄₈ Ni ₄₈ Cr₄，Co _50， Cr ₅₀。化学状态图谱已通过电化学测量和金相观察得到补充。Cr和Ni的含量约为 50％显着提高了在所有环境中的耐腐蚀性，而前者的有益效果更强。添加4％的Cr会产生轻微的积极影响，但碱性环境中的Co Ni系统除外，这与Co ₅₀ Cr _50一起，胜过其他成绩。在所有研究的合金-环境组合中，都会形成连续的氧化金属膜，其上的微米岛形形状和尺寸取决于特定的等级和侵蚀性条件。化学状态图的定量描述及其在通过羟基氧化物沉淀而形成的电化学相方面的理论解释，使岛型与伪钝化程度相关。