Saltwater is the ever-present, costly enemy of Navy ships – a major cause of corrosion. Silicone alkyd has been used for many years by the U.S. Navy; however, as a topcoat it did not offer long-lasting performance. When the military performance specification (MIL-PRF-24635) for weather-resistant exterior coatings added new high-durability classifications (Type V), it opened the door to alternative technologies that supported the Navy’s efforts to reduce the growing costs of corrosion by using coatings that offer longer service life, require less maintenance and can be cleaned versus repainted. Sherwin-Williams Polysiloxane XLE-80 HAPS Free epoxy siloxane meets these requirements.
When the amphibious assault ship USS Bonhomme Richard required exterior painting during a just-concluded 10-month maintenance period, Polysiloxane XLE-80 HAPS Free was chosen for the freeboard topcoat. It combines the properties of an epoxy and a polyurethane in one coat, providing superior corrosion protection, color stability and gloss retention.
A number of important cost- and time-saving advantages were gained as a result of using Polysiloxane XLE-80 HAPS Free. The dedicated drydock time for exterior painting was reduced because the polysiloxane system requires fewer coats (two instead of the traditional three plus a stripe coat). The excellent exterior durability provides the Navy the opportunity to reduce or eliminate future needs for sailors to apply maintenance paint for aesthetics – a common practice when silicone alkyd is applied as a topcoat. The silicone alkyd low solar absorption (LSA) formulas used by the U.S. Navy to reduce heat absorption into the vessels have a tendency to shift color from haze gray to pink over time. The “pinking” of Navy ships, never a favorite of the ship’s crew, is greatly reduced with the use of Polysiloxane XLE-80 HAPS Free technology. Now instead of maintenance painting, sailors can clean the freeboard instead. The Navy can also expect longevity of USS Bonhomme Richard’s new topcoat to be at least two to three times that of silicone alkyd.
Other features include:
- Low solar absorption (LSA) semi-gloss, self-priming;
- Color stability and excellent gloss retention;
- High solids (80% by volume);
- Low VOC content (<240 g/L);
- HAPS free; and
- Corrosion and chemical resistance.