Volvo Penta Zinc Cavitation Plate Anode | Martyr CM3855411Z Martyr zinc anode designed to protect the drive from corrosion in salt water. Volvo Penta cavitation plate anode Zinc anode for salt water applications Replaces Volvo Penta 3855411 Replaces OMC 3855411 For anti-spray anode see Volvo p/n 3857857 For aluminum see p/n CM3855411A For magnesium see p/n CM3855411M