PAINT DEFECTS

PAINT DEFECTS - PART A

SAGS

·        It is the paint defect of excess paint flow on the product surface.

·        It is caused due to improper mixture proportion of paint and thinner, irregularities on surface, too glossy surface finish and distance of paint spray nozzle gun and the working surface is too close.

·        This defect is rework by brushing out excess paint before curing the surface paint and by sander wheel or paper with less great size can rub on the defect and this portion will paint by a light coat.

ORANGE PEEL

·        It is the up and down that is irregular surface finish of paint, its skin looks like orange or lemon.

·        It is caused due to distance between paint spray nozzle gun and the working surface is too close, higher viscosity of the paint and the low air pressure.

·        This defect is rework by brushing out excess paint before curing the surface paint and by sander wheel or paper with less great size can rub on the defect and this portion will paint by a light coat. Clean the spray nozzle gun before use.

                                                   

OVER-SPRAY

·        It is look like a powder form and spread on the surface of product, that is painted surface having very less adhesion made due to some mistakes while doing painting.

·        The main reason of this defect is the higher degree of evaporation of the thinner which is mixed into the paint then if spray nozzle is too far away from surface being paint the thinner gets evaporate and only dry paint is attached to the surface.

·        It is rework by using thinner and brush to wipe out all dry paint from the work surface before curing of paint & after curing it should be remove by using grit paper of sander wheel and light coat is apply after rework.

                                   

COBWEBBING

·        It is look like a spider, the paint is spread like a spider, that is one thicker paint and another linings made from this point.

·        This is mainly caused due low degree of evaporation solvent mixed with paint and the painting surface is quite hotter than normal temperature then the solvent gets evaporated and only thicker paint is remaining that could not spread properly over the work surface.

·        Need to apply paint with slower evaporating solvent and the job should be at normal temperature or quite cooler than normal temperature.

·        Rework done by removing those spider like paint by using brush before curing and after curing by using grit paper of sander wheel and light coat is apply after rework.

                                                    

CRATERING

·        Cratering is the defect of pitting like structure of paint observed on paint surface.

·        It is caused due to air entrapped into the paint coat during painting and this air is blow out form paint.

·        It can be removed by using sander wheel or grit paper and after remove then apply the light coat on this surface.