Unfortunately, they prove to be erratic in their operation when re-installed and returned to use in a marine environment.
This type of failure is quite frustrating both to the owner and to the installer, service technician who has to cope with the type of intermittancies that cannot often be duplicated on the bench.
Physical Failures:
The most common physical failure results from corrosion eating away the parts of the connector holding the male and female components together. The result is that the connector simply disconnects. The cause of the corrosion is usually a lack of resistance of the connector body material and/or finish to the combination of salt/water and/or chemicals in the environment; but the corrosion can be hastened by the use of dissimilar metals. These are materials which are incomparable galvanically.
In spite of the general use of silicone greases, they themselves can introduce a form of connector failure, especially when exposed to salt. Where a silicone is present it can combine with the salt to form a thin, hard film of sodium silicate that is not only non-conductive, but very difficult to remove without damaging the connector. Even where silicon-based water-excluding gaskets are employed in the connector design, migration of the ethyl and methyl-silane based oils that are often added to the silicone rubber as softeners can cause problems. These are usually encountered where a connector is crimped to a cable.
Many physical failures take place because salt water has penetrated into that part of the connector where the wires are crimped or soldered onto the pins. Quite apart from the electrical effects of the corrosion products, these products frequently occupy much more volume than the metal upon which they feed. Occasionally enough pressure can be generated to rupture a shell that has already been weakened by corrosion.
Sometimes it is necessary to use a supplementary means of cable/wire strain relief in order to minimize the effects of wind-induced vibrations in the cable in causing a "grinding' action between the two halves of the connector.
Another Type of failure:
Dealing for the moment only with the part of the connector that is meant to disconnect and reconnect (and not with the parts that are attached electrically or other wise, to the cable) any connector may be broken down into a male-female or hermaphroditic component which is designed to mate with an equivalent part, an thereby pass electricity, and the parts needed to hold the former in alignment. The latter are usually insulators. In many connectors carrying Radio Frequency signals it is necessary to have the latter parts dimensioned so that the electrical impedance the connector is the same as that of the wire. Otherwise there will be a discontinue and a reflection will occur in the transmission system. This can reduce the effective radiating power of a transmitter, or cut the signal-strength of a received signal. Insulation leakage can cause loss of signal strength and/or unacceptable modification of the signal caused by line reflections. A good example of the latter is ghosts detail blurring in cable TV.
The result can be a radio, communication system, a GPS or Loran, or even a radio system that is unserviceable!
Where the RF impedance is not a consideration we still have to deal with losses in on the electrical insulation. Excessive leakage across the insulation will result in heating in high-power applications, insulation breakdown in high-voltage applications, signal leakage in multiple-pin control circuits. None of these are acceptable, and the consequences could be destruction of the connector and a fire hazard to consequential damages due to failure of a process-control, alarm, or communications system.
The introduction of corrosion products into the gap between the connecting pair connecting means can also result in problems ranging from rectification effects (most corrosion products can act like crude semiconductors) which can produce strange modulation distortion of the signals or even introduce spurious signals derived from the rectification of whatever RF (conventional RF of even fast rise time) signals ma be present in the environment. Generally this is characterized as excessive sensitive to "electronic smog".
As noted earlier, corrosion products can completely break the contact means through its increased volume, lock-up the connector so that it cannot be disconnected.
At the present cost of gold, where gold is used, it is applied in as thin a "flash" a possible consistent with low porosity. Even so, special processes must be used to minimize this porosity as will be evident upon reading almost any connector manufacturer's brochures.
Where gold is not used on both surfaces, the question becomes one of the compatibility of the connecting surfaces both with one another and with the intrusion environment. Often when less noble metals than gold are used in a contact pair and combined with sufficiently high contact pressure, they perform with greater reliability than gold to gold, or gold to ? at lower pressure. The key here is to have enough pressure to exclude oxygen and other contaminants.
Stabilant 22 (or either of its diluted form, Stabilant 22A - isopropanol or Stabilant 22E - ethanol) when used on a contact need only be present in a film thick enough to fill the interstices (or gaps) between the contact surfaces. Because of its switching ability, it will become conductive across these minute gaps without becoming conductive between adjacent pains or causing leakage across insulating surfaces.
The conductivity of a new connector will not be substantially improved by the Stabilant for the reason that there will probably be a sufficient contact-area already. Thus any added contact-area (aided by a material which has a higher volume resistance than the contacting metal) will be of minor consequence. However the Stabilant's presence will help to exclude oxygen and corrosive materials from the contacts, and its surfactant action will keep existing contaminants in suspension.
The action of Stabilant on an aging or older contact is somewhat different. Here the contact will not be as good; thus the conductivity of the Stabilant (once switched on) will appreciably lower any contact resistance.
On high current applications, the lowered resistance well may be enough to stop thermal runaway of the contact means, a situation where the heating of a joint causes expansion which by stretching the clamping means beyond their elastic limit results in a reduced contact pressure, increasing the resistance of the contact area, and further increasing the heating. In extreme cases this can literally cause a high current connector to explode.
Because of the "switching threshold effect", Stabilant will not "switch" to a conductive state between adjacent contacts and its "off" resistivity is high enough to prevent signal leakage.
Another potential problem in connectors is the area where the wire and or cable is connected to the contact means. Frequently the wire may be of solder or tin plated copper, while the rear of the contact body could be anything from gold-plate, through silver or tin plate, to an as-machined alloy. The introduction of solder itself on a bare copper wire can provide a potential problem of galvanic corrosion while some of the fluxes themselves can cause problems if they wick up into stranded wires. Then too there is the possibility that breakdown products from the cable jacket can cause corrosion of the copper.
Multiple point crimps, (made with properly designed tools) which insure that there is sufficient pressure on the conductors to absolutely exclude the entry of oxygen (and any contaminants as well) are often much more reliable than soldered joints besides having greater consistency, The Stabilants can be used to enhance the operation of such joints.
Because the polyolefin material looses its resiliency at low temperatures, leaks ma occur when its cold. We have seen this material used with rubber splicing compound (as used on high voltage connections) where a single layer of stretched splicing co pound is wrapped around the wire-connector-wire area before the heat shrink tubing is used. The elasticity of the splicing compound under compression is certainly better than that of any of the heat shrinkable materials and the resultant "booted joint" much less messy to open up.
A better method for environmental sealing to protect against the weather (as practiced by the U.S. Navy) is as follows:
This and other solutions are, of course, designed to exclude the salt and moisture from the connector and a choice of which treatment to use will be based on the location of the connectors, the ease of application of the treatment, and the life the materials used. Consideration must also be given to possible degradation of he shrink materials themselves by ultraviolet, ozone, or chemical contaminants.
One caveat; Where connectors operate under high-voltage conditions (such as on some power-amplifier tubes) it is advisable to confine the Stabilant coated areas to the actual contact surfaces.
The dilute form should be used for treating existing crimp type joints between multiple stranded wire and the contact.
Revision 2
NSCM/Cage Code - NATO Supply Code 38948
15 mL of S22A has NATO Part # 5999-21-900-6937
The Stabilants are patented in Canada - 1987; US Patent number 4696832. World-wide patents pending. Because the patents cover contacts treated with the material, a Point-of-sale License is granted with each sale of the material.
Stabilant, Stabilant 22, and product type variations thereof are Trade Marks of D.W. Electrochemicals Ltd.
© Copyright 1987, '88. '89, '90 - D.W. Electrochemicals Ltd. This note may be reproduced or copied, provided its content is not altered. The term "contact enhancer", © 1983 Wright Electroacoustics.
NOTICE: This Application Note is based on customer-supplied information, and D.W. Electrochemicals is publishing it for information purposes only. In the event of a conflict between the instructions supplied by the manufacturer of the equipment on which the Stabilant material was used, and the service procedure employed by our customer, we recommend that the manufacturer be contacted to make sure that warranties will not be voided by the procedures.
While to our knowledge the information is accurate, prospective users of the material should determine the suitability of the Stabilant materials for their application by running their own tests. Neither D.W. Electrochemicals Ltd., their distributors, or their dealers assume any responsibility or liability for damages to equipment and/or any consequent damages, howsoever caused, based on the use of this information.
Stabilant, Stabilant 22, and product type variations thereof are Trade Marks of D.W Electrochemicals Ltd.