The use of platinised titanium anodes in chrome plating applications in the aircraft industry by Peter Morrell and Joerg Wurm, Composite Metal Services, Shipley, England and Metakem GmbH, Usingen, Germany

Advantages and disadvantages of chrome plating The mechanical and chemical properties of Cr the simplicity of the electroplating process Disadvantages A very poor electroplating efficiency and a bad throwing power of the bath

Demands for making a perfect chrome coating Shaped anode with small anode-cathode gap Assembly of anode and component outside the bath Good current distribution in the anode because of the small anode – cathode gap Good electrolyte exchange to maintain chrome concentration and to extract the bubbles Safe and good contact to the component especially for high current applications

Benefits of working with platinised titanium anodes Remains active for a large number of coating cycles Shaped (conforming) anodes allow ‚ better‘plating to size Platinised titanium mesh anodes facilitate the electrolyte exchange Allows to solve complex plating tasks like simultaneous plating on a multiple of faces and reduces the number of heat treatment cycles

Plating the inside of a recessed volume

Plating of a welded-on flange

Plating of a ball-and-socket joint

Plating of six cylindrical faces of an axle

Comparison of plating with lead anodes (upper part) and with cylindrical platinised mesh anodes (low)

Plating on nine faces in one cycle of the ‘Sliding tube’ Barrel part for shock absorption Left axle Right axle Brake flange

Assembled ‘Sliding Tube’ with Pt/Ti anodes over the plating tank

Benefits of using conforming anodes for the example plating of the ‘Sliding Tube’ Reduction to a single assembling operation Single de-imbrittlement cycle Large reduction of the grinding/ resizing effort Shorter total plating time and plating tank occupancy Overall reduction of maintenance time Overall reduction of manpower for maintenance

The future of chrome plating Chrome plating can be processed without hazards to health and environment with a safe technology Chrome coatings itself are not toxic and there is no argument against using them Replacing chrome plating by CVD, PVD or spraying is possible but not flexible compared to electroplating The aim should be to look for another electroplating process with properties comparable to chromium

Thanks We thank Messiers Dowty, Messiers Services, Lufthansa and Smiths Aerospace for allowing us to present samples of their daily tasks. We appreciate that very much as it demonstrates to many users who still plate 100 microns to a pieces and grind it down to a homogeneous layer of 50 microns what can be improved in their plating process. We specially thank Mr. Knauthe for making the drawings and of course you for your patience.