Участник:Rautredsujec
Facts You Should Know About Corrosion Control & Protection
Protective Coatings
Anti corrosive pigments are:-
a) Red Lead
b) Zinc Chromate
c) Zinc Phosphate
d) Zinc Dust
Preventing corrosion involve minimizing the flow of corrosion current in order that if negligible current, negligible corrosion result. Resins with highest electrical resistance are, catalyzed epoxy, phenol, vinyl and chlorinated rubber. Inclusion of pigments such as talc, china clay, mica and iron oxide also help out with enhancing the resistance.
Removing soluble deposits around the steel surface is necessary as their presence will short circuit the resistance with the paint film to stage where rusting can take place. The thicker the coating the larger would be the electrical resistance. Coatings limit the access of oxygen, water and salts and so control corrosion in this way with a purely barrier effect. Catalyzed epoxies, coal tar epoxies, polyurethane, vinyl's and chlorinated rubber coatings possess the lowest permeability to water and oxygen.
Alkyd and oil based coatings will be more permeable to corrosive agents than top rated coatings specified to make certain all corrosive substances are taken from the steel surface and maximum adhesion is achieved involving the coating and steel. The coatings chosen or specified needs to be ideal for environmental surroundings, characteristic and purpose the substrate is subjected.
For purpose to avoid and resist causes by:-
a) Chemical spillage
b) Chemical fumes
c) Temperature
d) Skid resistance
e) Abrasive resistance
f) Oil resistance
g) Fire-proof
Types of Coatings
Normally coatings are conventional coating systems or powerful systems. The conclusion on the type of coating to use depend upon the price and budget one have plus the expected life or time period of the coatings and the required function of the coatings, because of the security, decoration or coding purposes, etc.
For coding and decorative purposes, conventional systems usually are recommended but also for protection purposes, powerful systems are suggested. Conventional coatings usually are one pack product whilst high performance coatings come in two packs. Single pack product are usually air drying, two pack products normally cure by chemical reaction about the base through the catalyst or hardener.
For the best results, it's always best to consult they who will be specialised in manufacturing certain array of coatings. Some are specialised in decorative coatings for houses, or protective coatings for industrial purposes or marine coatings vessels and ships or automotive coatings for vehicles or special coatings for appliances or air crafts. See a right manufacturer for the ideal sort of coatings needed.
Sort of Application
Application can be done by brush, roller, conventional spray or airless spray. Brush and roller are widely-used where condition won't allow air or airless spray. Not suitable for top build coatings or achieve high film thickness. Slow in process and coverage is about 180m2 to 380m2 per man day. Conventional spray is acceptable for decorative and coding as only thin film is possible.
For cover purposes, airless spray is usually recommended which is the quickest technique of application. Covers 750m2 to 1100m2 per man day. Charge of application is actually tip size and input and output pressure. Can be used for most paint types and will achieve high film thickness.
Application Condition
Paint really should not be applied to adverse conditions, like temperature below 5 degrees C and never above 35 degrees C. Not in a windy condition or when surfaces are wet on account of rain, snow, ice, fog or condensation. Allow painting only when surface climate is 3 degrees C higher than the dew point.
Paint Mixing
Every new tin of paint opened must be mixed thoroughly which has a stirrer to disperse the solids. In 2 pack products, to make sure that the camp and hardener can chemically react together and cure, always employ an analog mixer. Always mix base and hardener inside the correct ratio.
Paint Thinning
Use thinners only once necessary. Make use of the correct thinner to the product. Avoid greater than 5% by volume of thinners. Too much use may cause solvent entrapment, runs, sags, slumping, retard cure and affect wet film thickness and dry film thickness ratio.
Pot Life
All two pack products have a very pot life. That's time period between mixing and curing once the paint is workable and can be applied. Pot life's temperature related. Never mix a lot more than can be used before pot life expires. Exceeding pot life will waste paint and can block up airless spray equipment.
Airless Spray Procedures
Check tip size and output pressure. Hold spray gun 30 cm to 45 cm through the surface. spray gun to become parallel to come to light 90 degrees as a result. Horizontal pass 50 cm to l meter. Overlap previous ignore 50% if at all possible to make certain even film thickness. Trigger to be released after each pass. Cross hatching appropriate for even film thickness.
For more info about ESM Resin view this resource.
