posted on May 13, 2013 14:13
Pipe Repair | Corrosion Repair
Corrosion under insulation, galvanic corrosion, alkaline acidic corrosion and stress corrosion cracking have all been known to happen in certain conditions. Metal loss, leaks and damage eventually occurs if the corrosion is not addressed. Intruding water is one of the major problems in CUI. Moisture could be external but could also be present in the insulation. Corrosion could attack hardware, jacketing or the piece of equipment under the insulation. The rate of corrosion attack is usually based on the environment/weathering, vibration, type of metal surface, wet insulation, abuse from people and concentration levels of water and or chemicals. Keeping liquid from penetrating the insulation is the major factor preventing CUI. Maintenance, selection of insulation, the design of the equipment, protective coatings and weather barriers are all used to prevent this corrosion. When insulation is removed and inspected, sections of metal could need repair. Pitting corrosion is a small area of corrosion that takes the form of cavities. If there are dents, dings or deep pitting present, a repair is then warranted.
If the surface is to be coated and the temperature is below 350F, Lab metal can be used to fill in deep pitted sandblasted surfaces and top-coated with Thurmalox 218/219 for under insulation. If the temperature exceeds 350F and is under 1000F, Hi Temp Lab metal can be used to fill surface imperfections and top-coated with two coats of Thurmalox 225HD for under insulation.
If there is a deep pitted surface inside a tank/vessel and the immersion temperature for the vessel has a maximum immersion temperature of 500F and contains mostly water,
Prior to the application of the Dampney Apexior 1, Dampney recommends that the interior vessel surfaces be high pressure washed to remove contaminants and then abrasive blast cleaned, using the Surface preparation procedures detailed on the attached Apexior Number 1 Technical Data Sheet.
The next step is to apply the Dampney Hi Temp Lab Metal up to ¼ inch thick to fill in all voids, pits or deep surface imperfections. Allow the Hi Temp Lab Metal to cure for a minimum of 24 hours prior to the application of the Apexior 1C Internal Lining System (which is to be done per the requirements and curing procedures defined in the Dampney Technical Data Sheet).
Dampney Company, Inc.
85 Paris St.
Everett, MA 02149
(617) 389-2805 FAX (617) 389-0484