10.4.3 电镀铜覆钢（镀铜钢、铜镀钢）
电镀铜覆钢为三类中质量最为可靠的一类，目前仅有电镀铜覆钢通过了国际权威的美国UL467标准认证，具有以下其他类产品所不具备的优势：
1）厚度 任一点铜层厚度不小于0.25mm。
2）延展性 一端固定，在距其40倍距离处，施加与之垂直的作用力，使其永久性弯曲成30°，铜层应无剥落或翘皮开裂，表面无任何裂痕或者明显厚薄不均的现象。
3）附着力 能车床切削，由铜层表面往内部切削，使其小于原有直径1mm，切削到足以暴露铜层与钢棒连接处，铜层不得有剥落和脱落现象。
UL467中有关镀铜钢标准的部分内容如下（英语）：
6.1.2 A grounding or bonding device marked for direct burial shall be pro-vided with all screws necessary for assembly or connection of the device，and all components shall be constructed of：
a）copper or a copper alloy containing not less than 80%copper；
6.9.2.6 The copper coating shall not be less than 0.25 mm（0.010 in）thick at any point and shall comply with the adherence requirement in Clause 7.7.1 and the bending requirement in Clause 7.7.2.
7.7.1 Adherence of coating
There shall be no separation of the coating from the steel core when subjec-ted to the test described in Clause 9.7.1.Peeling of the coating by the steel plates or the jaws of the vise shall be allowed.
7.7.2 Bending
There shall be no cracking of the coating when subjected to the test de-scribed in Clause9.7.2.
9.7.1 Adherence of coating
A457 mm（18 in）length of the rod with one end cut to a 45°point shall be driven between two steel clamping plates or the jaws of a vise set 1.02mm（0.04 in）less than the diameter of the rod，so as to shear off suffi-cient metal to expose the bond between the coating and rod.
9.7.2 Bending
A length of the rod shall be rigidly held in a clamp or vise.A force shall be applied normal to the free end of the rod at a distance from the clamping device equal to 40 times the rod diameter.The application of force shall be such that the rod is permanently bent through a 30°angle（see Figure 2）.
电镀铜覆钢之所以具备上述优势原因有如下两点：
•四维连镀工艺易于掌控，可以确保铜层的均匀性。
•尽管铜、钢结合力差，但两者均与可与镍很好地结合，故而在铜层和钢芯之间镀上一层镍，就能实现可靠的原子连接，从而确保高质量的延展性和附着力，避免铜层开裂、翘皮和脱落现象。
因此，如果需要确保铜覆钢的质量可靠性，那么，通过美国UL467标准认证者为最佳选择。