Following is the text of an article bearing the same title taken from the US FAA publication General Aviation Alerts, AC43-16, Alert Number 130 of May 1989. It is of particular interest regarding the specific instances it covers: however, it is yet another example of the inadvisability of proceeding with local modification of even the simplist nature without proper approvals. [ad]
An American turbine engine manufacturer recently published a service letter alerting operators that wrapping stainless steel tube assemblies with a chloride-based material, such as neoprene tubing and fibreglass tape to prevent chafing, has resulted in premature tube failure. A chloride-based material breaks down from the presence of high engine temperatures and attracts moisture, resulting in the formation of salts which are highly corrosive to stainless steel tubes. After a period of time, stress cracking develops resulting in failure of the tubes. Additional investigation along the same lines by a foreign engine manufacturer revealed that titanium is also affected by the chemical reaction between chloride-based materials when operating in temperatures in excess of 150 degrees C (302 degrees F).
A related problem is the use of chloride-based packaging material, such as PVC sheeting (plasticized polyvinyl chloride) as a packaging material. This can result in chloride-based residue being left on the component, possibly leading to the sort of failure described above.
In summary, operators are reminded to follow the engine manufacturer’s publications in installing stainless steel engine air, oil and fuel tubes and warned against using chloride-based materials on any stainless steel or titanium components, whether installed on the engine or held in storage
