6. JACKPOINT COATING MATERIALS AND PROCESSES
The 3M Company warned a year back that it would be withdrawing Fluorad FC 722 from the market worldwide and recommended that all users submit a "last order" to purchase a full year's production requirements. The aim was to tide them over pending the availability of a replacement compound.
Despite the warning, supplies have not yet ceased and jackpoint manufacturers have been able to continue to order Fluorad. Nevertheless, it still appears that 3M will discontinue production some time in the future, probably about mid-2002.
Telecom looked into other alternatives and contacted a UK manufacturer, Acota Ltd (previously named Layton Co Ltd), which manufactures a coating called "Certonal TL6x". As this has properties identical to those of Fluorad FC 722, we have defined this material as an accepted alternative for the production of Telepermitted 2-wire jackpoints.
However, some important developments came to light during our investigations after we had noted an apparent increase in failure rates relative to the original trials and were looking into reasons for this. What is now very clear is that full protection is only available by closely controlling not just the cleaning and coating, but also the drying process. Cleaning, drying and the subsequent dipping process have been found to be even more critical than was indicated in PTC 223. This applies, independent of whether the coating is Fluorad FC 722 or Certonal TL6x.
In almost all failures, corrosion occurs in the area each side of the BT 601A separator where the contact springs and lead wires emerge. Exposure of base metal due to cracking of the spring plating is also common in the same area, where the springs are subjected to the sharpest bending. It is thus particularly important that the coating adheres in these areas. Nevertheless, the coating will only adhere if the surfaces are thoroughly clean and dry.
The complex shape in this area makes it more difficult to clean effectively. It can also be much slower to thoroughly dry because of trapped water, then any trapped moisture or air makes it difficult to coat completely in this critical area while the jackpoint assembly is immersed in the coating compound.
Another key factor is close production control of the percentage of solids in the coating material. Too much and the coating does not enter any plating cracks, too little and the coating does not provide the needed level of protection. There is also the problem that post coating handling can damage the coating film, especially before it is totally dry.
These matters are being addressed in a revised specification, full details of which will be published on the Access Standards website in the near future.
DOUG BURRUS
Manager
Access Standards
