Cadmium Substitution - garteur

GARTEUR LIMITED
2 Coatings evaluated
An important feature of cadmium plating is its ability to provide sacrificial protection if it
becomes damaged in service. In considering the range of coatings that might be
substituted for cadmium only coatings that would provide sacrificial protection were
selected. Thus nickel plating, which can provide a high level of corrosion protection, was
not chosen as the coating is more noble than steel and gives no protection once the
coating is damaged. Details of the coatings evaluated together with the method of
application are given in table 1.
The coatings are either aluminium or zinc based and with the exception of the
unbalanced magnetron sputtered aluminium - magnesium coating are available
commercially. Electro-deposited cadmium plating has been included in the programme
as a reference.
The coatings were applied to 150mm x 100mm panels cut from 1mm thick 4130 steel
sheet. These panels were used to evaluate the corrosion resistance of the coatings and
properties such as paint adhesion and resistance to aircraft fluids. A series of fasteners
were also coated to allow torque-tension and electrical conductivity measurements to be
made. Fatigue specimens and hydrogen embrittlement test pieces were machined from
4340 steel rods and subsequently plated.
Detailed information regarding the application of the various coatings is given in Annex
A.
GARTEUR SM/AG17 TP128 Page 3