Su Bin

(Beijing Jinxiu Silk Road Agricultural Science and Technology Limited Company,Beijing,100000)

Abstract:At present,the hot-melt highway guardrail refurbishment paint used in the current market does not have the conditions for on-site renovation.It is necessary to dismantle the old guardrail and have high requirements for heating heat source,which does not comply with the national environmental protection policy.The invention relates to a novel water-based self-drying paint capable of self-drying film formation under cold and normal temperature conditions without baking and has the characteristics of abrasion resistance,scratch resistance and scratch resistance.It is suitable for various spraying equipment such as spraying,rolling coating,dip coating,brush,etc.Curing at room temperature without professional tools such as UV and baking equipment,it can greatly reduce the cost of conventional production.It is environmentally friendly,non-toxic,green and healthy and is easy to recycle without generating secondary costs and environment pollution.

Keywords:water-based self-drying paint;road guardrail renovation;technology innovation

I.Analysis on the Routine Treatment Process of Highway Guardrail

The highway guardrail is the main form of the semi-steel guardrail.It is a continuous structure in which corrugated steel guardrails are spliced to each other and supported by the main column.The surface treatment of highway guardrails is divided into three types:hot-dip galvanizing,cold-galvanizing and spray-coating.

Hot-dip galvanizing is also called hot-dip galvanizingor hot-dip galvanizing.The rust-removed steel is immersed in a zinc solution melted at about 500°C to keep the zinc layer to the surface of the steel member,thereby it can prevent corrosion.The process of hot galvanizing is as follows:finished product pickling-washing-adding coplating solution-drying-hanging plating-coolingdosing-cleaning-polishing-hot galvanizing.

Cold galvanizing is also called electro-galvanizing.It is an electrolytic device that removesoil,picklesand then putsit into asolution of zinc salt.It is connected to the negative electrode of the electrolyzer.The zinc plate is placed on the opposite side of the pipe and connected to the electrolysis.The positive pole of the device is connected to the power source and a direction of movement from the positive electrode to the negative electrodeisused todeposit alayer of zinc on thepipe member and the cold-plated pipe member is processed and then galvanized.Cold-galvanized coatingsaremainly anti-corrosion by electrochemical principle.It is necessary to ensure sufficient contact between the zinc powder and the steel and the electrode potential difference is generated,so the surface treatment of the steel is very important.In theory,electro-galvanizing can reach or exceed the thickness of the zinc layer of hot-dip galvanizing.However,in general,thin electroplating generally leads to poor anti-corrosion and anti-rust effect with short protection life and poor anti-scratch effect,but itscost isrelatively low and it hasbright appearance.

Spray molding is a surface treatment method in which plastic powder is sprayed onto a part.Spraying molding is also the electrostatic powder coating that we often talk about.It uses an electrostatic generator to charge the plastic powder,adsorb it on the surface of the iron plate and then bake it at 180-220℃to melt and keep the powder to the metal surface.Spray plastic products are mostly used in indoor cabinets and the paint filmhas a flat or matte effect.The spray powder mainly includes acrylic powder,polyester powder,etc.The utility model hasthe advantages that no thinner material isneeded,the construction has no pollution totheenvironment and it isnon-toxic tothe human body.Theappearance quality of thecoatingis excellent.The adhesion and the mechanical strength are strong.The curing time of the spraying construction is short and the corrosion resistance and wear resistance of the coating is much higher without using Primer.It has simple construction,low technical requirements for workers and it has lower cost than that of painting process.Some construction occasions have clearly stated that it is necessary to use the electrostatic spray process and the common flow phenomenon in the painting process will not occur during the electrostatic spray coating process.This type of technology is used to treat the surface of the wave guardrail.Under normal circumstances,there are three forms-direct steel plate spray,cold-galvanized steel plate spray and hot-dip galvanized steel plate.

For the renovation of highway guardrails,the above processes do not have on-site renovation conditions.After the highway guardrail is outdated,most of them can only be removed and replaced,which will increase the cost of secondary demolition and installation,increase labor and transportation costs and cause inconvenience of expressway traffic and thecomprehensivecost ishigh.

At present,there are some hot-melt highway guardrail refurbishments on the market,but there is no on-site refurbishment condition and the old guardrail needs to be removed and the heat source is required to be high.Some solvent-type highway guardrail refurbishment paints,such as fluorocarbon paint,need to be baked for two coats and two bakes,three coats and two bakes.Its baking temperature is 150-170℃for film formation and its baking time is within 20 ～40min,which it cannot implement on-site renovation construction.

Since the surface of the highway guardrail is galvanized,the refurbishment paint is not easy to be directly applied and the adhesion after brushing is insufficient,resulting in peeling off the skin in a short time.At present,the refractory paint on the market has insufficient surface hardness,poor scratch resistance and poor weather resistance,durability and corrosion resistance.So far,there is no refurbishment paint for highway guardrails that can meet therequirements.

II. A New Type of Water-based Self-drying High-speed Guardrail Renovation Paint

(i)Functional Features

The new water-based self-drying high-speed fence renovation paint can self-dry film at room temperature without baking.The hardness of the coating film is as high as 2H to 9H and the abrasion resistance and scratch resistance(scratch resistance)are superior.The coating film has excellent performances such as antifouling,antibacterial and anti-fingerprint and is not easy to be soiled and convenient for care.The coating film has high transparency,high gloss,high mirror surface,good finishing effect,smooth and delicate surface,rich and comfortable hand feeling.Resin particles are small with excellent adhesion.They can be used with a variety of primers and they are not easy to peel off,which isa good primer and topcoat coating.

The paint owns superior performances such as rust-proof,anti-slip,acid-base salt,anti-corrosion,waterproof and hydrophobic,anti-liquid penetration,mildew resistance,high temperature non-combustion(700℃),UV aging resistance,electrical insulation and so on.It is a one-component liquid product that is no need to add curing agent.It is to operate and its construction tools are simple.It is also suitable for spraying,roller coating,dip coating,brush and other spraying equipment.The paint is cured at room temperature,without the need for professional tools such as curing equipment as UV or baking or even professional technicians,which can greatly reduce the conventional production cost,environmental protection,non-toxic,green and healthy with no pollution to the environment and convenient for waste recycling.It doesn’t producesecondary cost aswell.

(ii)Preparation Technology

The paint preparation technology is very simple and does not require special large equipment.

First,the powder(zinc powder or color paste)and all the additives (except the defoamer)are dispersed at a high speed.The rotation speed is 800-1200 and the dispersion time is 45-60 min to obtain thedispersion liquid.

The second is to add the resin to the dispersion liquid with low-speed stirring(hand stirring can also be used)for 10 minutes and adding defoaming agent for 5 minutestotest thedischarge.

(iii)Construction Technology

Surface deducting→base rust curing anti-rust treatment→spraying (brushing or roller coating)renovation paint→ inspection acceptance.The coating film thickness is 100～200um.The drying speed of the product is adjustable,which the quick drying can bedried in 1min,or it can be dried slowly within a few hours.

Figure Spraying Equipment Airless Sprayer

The airless sprayer uses a special electric,pneumatic or other power to drive the high-pressured pump to form a high pressure of 150-350 Kg/cm2for the paint and instantaneously ejects through an airless nozzle of a special shape and structure to form a very fine fan-shaped mist.The spray rate of the coating was 0.9 m/sec.All the paint is quickly sprayed onto the surface of the coating without rebound and splashing,which not only saves 40%of the paint,but also has almost no paint mist.It can be sprayed without wearing a mask,thus it can reduce pollution and protect the environment.Since the effect of high pressure is 10 to 50 times higher than that of the conventional spraying machine and the spraying speed is as high as 200 to 600 square meters per hour,which not only the coating quality can be ensured,but also the coating cycle can be greatly shortened and ensured.The coating quality is bright and flat.At the same time,it can spray high-viscosity coatings and can save thinner materials or no thinner during spraying.It can reach a thin coating of 0.05-0.25mm or even a thick coating of 1-2mm without air-spraying.Because there is no rebound force in the airless spray,it is easy toenter thecornersand edgeswhen sprayingthe corners and edges,so that it hasa uniformbright and smooth coating.Since the coating atomization mechanismisformed into a mist by the high pressure of the coating itself and the atomized state coating does not contain compressed air,it is called airless spraying.

(iv)Application Examplesand Test Indicators

From June 6th to June 11th,2017,three professional workers applied this product to the construction of 1000x4 meters in the Yanjiao section of Jingping Expressway.Without disassemblying the guardrail,the mechanical spray paint was used for 3 days and sprayed twice to form a dry film of 100um.The test indicator results are as follows.

Main Indicatorsof Water-based Self-drying High-speed GuardrailRenovation Paint Test

III.Conclusion

The water-based self-drying high-speed fence renovation paint is a high-quality steel anti-corrosion coating with a dry film zinc content of 35%.It adoptsimported high-purity zinc powder and special resin and additives.It has strong cathodic protection and corrosion resistance.It is easy to construct.It can be dried in 1 minute at the earliest.The dried paint film has a bright surface close to hot-dip galvanized surface,which is silver and has sturdy film with good adhesion.The product can be widely used for anticorrosion of varioussteel products and structures,rust protection of various metals,repair of leakage plating of hot-dip galvanized parts,hot-dip galvanizing of materials such as small hardware and mechanical components and replacement of electroplating processes and anti-corrosion and decorative treatment of large components that are not hot-dip galvanized.It can also be used for surface decoration of other materials such as wood,plastic and glass.Its distinctive features are fast self-drying,bright silver with close to hot-dip galvanizing,high-purity imported zinc powder,strong anti-corrosion ability,strong film,scratch-resistant,in line with EU RoHs heavy metal content standards.