Wash Primer Research Articles

The Effect of Aluminium Surface Treatments on the Bonding Properties of Silica-Modified Epoxy Adhesive Joints: A Statistical Approach

A full factorial design is carried out to investigate the effects of different surface treatments, the inclusion of silica microparticles and the use of wash primer on the apparent shear strength and adherent strength of single-lap aluminium joints. Scanning electron microscopy, surface energy and roughness measurements are performed to characterise the aluminium surface. The results show that the use of wash primer decreases the apparent shear strength of the joints significantly. The cohesive failure of the primer is the main cause of the reduction in strength. On the other hand, the inclusion of 10 wt.% of silica microparticles in the adhesive layers increases the shear strength by 26%. Surfaces treated with NaOH for one minute, without using a wash primer, result in the most resistant joint. In contrast to the apparent shear strength, adherent strength is most effective when only degreasing is considered.

Sustainable Sandwich Panels Made of Aluminium Skins and Bamboo Rings

This work investigates the mechanical behaviour of a sustainable sandwich panel, consisting of bamboo rings core, treated aluminium skins and epoxy adhesive. A Design of Experiment (DoE) is used to identify the effects of bamboo diameters (30 and 45 mm) and aluminium skin treatments (alkaline degreasing and application of primer) on the mechanical and physical properties of sandwich panels. The aluminium skins treated with the wash primer significantly increase adhesion to the polymer, resulting in greater maximum load, flexural strength, maximum skin stress and maximum core shear stress; while the skins treated with NaOH resulted in a greater flexural and core shear modulus. Relatively more rigid and resistant structures are obtained with Ø30 mm rings, due to the increased surface contact area and the number of constraints on the core. The samples fail due to the skin fracture, implying an efficient face-core bond that is attributed to the proper absorption of the polymer by bamboo and the treatment of the aluminium surface. The proposed panels present good mechanical performance, proving to be a feasible and promising alternative for secondary structural applications.

Study of the anticorrosive properties of “quebracho colorado” extract and its use in a primer for aluminum1050

Tannins have been used to replace chromate in wash-primers as a temporary (“in transit”) protection for metals. In the present work, the anticorrosive properties of “quebracho colorado” tannins were tested in water solution and in wash primers to protect aluminum alloy 1050. Polarization curves (linear and Tafel) and corrosion potential measurements were done on the alloy in contact with different concentrations of the tannin. A tannin wash primer was prepared and coated panels were tested in 100% humidity chamber (ASTM D 2247) and by electrochemical techniques (linear polarization curves, corrosion potentials and ionic resistances). Chromate and talc primers as well as no-coated aluminum alloy were also tested, as control, to compare the results.

Study of zinc tannates prepared with Tara powder (Caesalpinia spinosa) as anticorrosive pigments in alkyd paints and wash primer formulations

Abstract The aim of this research was to evaluate the anticorrosive properties of alkyd paints and wash primers formulated with zinc tannates containing Tara tannins. Their inhibitory efficiency was compared with paints pigmented with well-known anticorrosive pigments by accelerated corrosion tests (salt spray test, Prohesion test, and sulphur dioxide test), natural exposure tests and some electrochemical techniques (corrosion potential, polarization resistance and impedance measurements). It was demonstrated that the capacity of inhibiting corrosion of zinc tannates is equivalent to that shown by most commercially available conventional pigments, such as zinc phosphate and zinc chromate.

Laboratory and Field Studies of Poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAM-PPV): A Potential Wash Primer Replacement for Army Military Vehicles

In this study, an electroactive polymer (EAP), poly(2,5-bis(N-methyl-N- hexylamino)phenylene vinylene) (BAM-PPV), was tested as an alternative to current hexavalent chromium (Cr(VI))-based Army wash primers. BAM-PPV was tested in both laboratory and field studies to determine its adhesive and corrosion-inhibiting properties when applied to steel and aluminum alloys. The Army Research Laboratory (ARL) tests showed that BAM-PPV combined with an epoxy primer and the Army chemical agent-resistant coating (CARC) topcoat met Army performance requirements for military coatings. After successful laboratory testing, the BAM-PPV was then field tested for one year at the Aberdeen Test Center (ATC). This field testing showed that BAM-PPV incorporated into the Army military coating survived with no delamination of the coating and only minor corrosion on the chip sites.

Intrinsically Conducting Polymer-Based Heavy-Duty and Environmentally Friendly Coating System for Corrosion Protection of Structural Steels

ABSTRACT This work investigates the potential use of an intrinsically conducting polymer—polyaniline—that, when mixed in polyvinyl-butyral and top-coated with an acrylic resin layer, demonstrates comparable performance to the existing coating systems, according to the experimental data from two ASTM standard tests performed to evaluate its overall corrosion durability and tensile adhesion (pull-off strength). Formulation of the polyaniline-based wash primer was provided. Scanning Kelvin probe force microscopy (SKPFM) was used to analyze the microscopic mechanisms of the superior performance. The polyaniline-based primer demonstrated potential surface ennobling and oxygen smearing-out capabilities in this study. Under the protection of a top coat, the primer provided both preventive and corrective protection in a smart mode. The layered structure including an ICP primer, as demonstrated in this study, constitutes a viable smart coating system for corrosion protection of metallic materials.

Painting rusted steel: The role of aluminum phosphosilicate

Surface preparation is a key factor for the adequate performance of a paint system. The aim of this investigation is to employ a wash-primer to accomplish the chemical conversion of rusted surface when current cleaning operations are difficult to carry out. The active component of the wash-primer was aluminum phosphosilicate whose electrochemical behavior and the composition of the generated protective layer, both, were studied by electrochemical techniques and scanning electron microscopy (SEM), respectively. Primed rusted steel panels were coated with an alkyd system to perform accelerated tests in the salt spray chamber and electrochemical impedance measurements (EIS). These tests were conducted in parallel with a chromate wash primer and the same alkyd system. Results showed that the wash-primer containing aluminum phosphosilicate could be used satisfactorily to paint rusted steel exhibiting a similar performance to the chromate primer.

Six-Year Evaluation of Thermal-Sprayed Coating of Zn/Al in Tropical Marine Environments

The main objective of this research was to evaluate the performance of thermal-sprayed coating of Zn/Al (double layer) after six years of exposure, with and without the use of sealant (wash primer) in tropical marine environments of very high aggressiveness: La Voz Station (located at the Peninsula de Paraguaná/Falcón State) and Lake Maracaibo Crossing Station (located at Zulia State), in Venezuela. To that effect, carbon steel coupons (100 mm × 150 mm × 2 mm) were sprayed by flame process. The coupons were characterized by means of initial weight, thickness, metallographic, adherence, and roughness, being evaluated monthly by visual inspection during six years. After removal, the coupons were evaluated by microscopic analysis to determine the morphology of attack, microstructure, penetration of contaminants, composition, and morphology of corrosion products. The results showed that after six years, the double-layer system represents an excellent choice for corrosion protection of steel by combining the galvanic protection of zinc with the erosion resistance of aluminum. However, due to the erosion-corrosion effect, a sealant such as wash primer can be used in order to extend its service life.

Paint pretreatments for aluminum

Chemical conversion coatings are the most widely used prepaint treatment processes for metal substrates. Processes specifically designed for aluminum are of recent origin. These include accelerated chromate phosphates, chromate oxides, anodizing and, very recently, nonchromate formulations. Historically, however, phosphoric acid cleaners, wash primers, and iron and zinc phosphates have all been utilized as paint pretreatments with satisfactory results. Among these, the chromate types provide the most reliable underfilm corrosion protection and paint adhesion. Anodized coatings, especially unsealed sulfuric and chromic acid types, are also comparable in performance, but fall far short of the productivity and cost effectiveness of the chromate processes. A careful evaluation of critical product requirements is essential in selecting the right conversion coating for anticipated field performance. Paint pretreatments must assure these corrosion protection functions passivation of base aluminum, action as a barrier against moisture, oxygen, and other corrosive agents, electrochemical insulation, and protection against mechanical erosion. In addition, conversion coatings must provide other essential interfacial properties complementary to the paint top coat, including an effective and continuous bonding site; chemical stability during the service life of painted products; remaining insoluble, impervious, and flexible; providing a wettable subsurface for paint application; and maintaining adhesive integrity between the base metal and painted film. See Table 1 for typical performance data.

An environmentally acceptable primer for galvanized steel: Formulation and evaluation by SVET

The object of this paper was to formulate a two-pack wash primer employing aluminium phosphosilicate as active anticorrosive pigment instead of basic zinc chromate. The anticorrosive action of the primer was evaluated by the polarization technique and the scanning vibrating electrode technique (SVET). The exposed surface was then examined by scanning electron microscopy (SEM) and the surface composition determined by energy dispersive X-ray (EDX) analysis. The primer was finally integrated in a complete paint scheme whose anticorrosive performance was evaluated by the salt spray chamber and electrochemical impedance spectroscopy. The adhesion of the primer plus a painting system was also evaluated by standard ASTM D 3359-90 test method. The wash primer pigmented with zinc chromate was used as reference. Results indicated that basic zinc chromate could be replaced by the more eco-friendly wash-primer containing aluminium phosphosilicate.

Corrosion protection of galvanized iron by polyaniline containing wash primer coating

Wash primer treatment of galvanized iron (GI) structure is widely used before painting in order to improve adhesion. Traditional wash primer contains zinc tetroxy chromate. Due to hazardous nature of chromate, alternate compounds for chromate replacements have been identified. In recent years polyaniline containing coating has been found to protect GI. In this study, a wash primer based on polyaniline has been formulated and its corrosion protection ability of GI has been compared with that of traditional chromate based wash primer by salt spray and EIS test. It has been found that the polyaniline based wash primer is able to protect GI and its corrosion protection performance is similar to chromate based wash primer coating.

Recent Development of Vegetal Tannins in Corrosion Protection of Iron and Steel

Inhibitors are employed predominantly for corrosion control in closed systems, as a cost-efficiently alternative to the use of high corrosion-resistant materials. Due to the environmental requirements that are currently imposed on the development of cleaner inhibitors, vegetal tannins, a class of natural, non-toxic, biodegradable organic compounds that can be obtained at reduced cost has been proposed. This review relates recent uses of several vegetal tannins in corrosion protection, particularly as corrosion inhibitors of iron and steel in acidic and near neutral media. Several methods of inhibition efficiency evaluations along with their action mechanisms are discussed. The present review presents some important patents in the development of vegetal tannins in corrosion protection of iron and steel. In many industries, the need to use constructional mate- rials safely, but cost-effectively, is a primary consideration. Frequently, physical requirements can be satisfied easily, but corrosion effects seriously complicate the selection of suitable materials. Generally, increased corrosion-resistance can only be obtained at increased cost. However, the actual material-related costs incurred in a project will depend on the corrosivity of the environment concerned, the required design life, the physical requirements of the material, and the readily available stocks. In some cases, appearance may also dictate the use of a more expensive material. The costs and problems associated with corrosion-resistant materials means that, in many cases, the use of corrosion inhibitors is a prac- tical and economic alternative. Industrial use of corrosion inhibitors is, therefore, now broad based and extensive. Proper surface preparation is the key to obtaining good performance by a surface coating. The major problem in preparing a metal surface is the removal of all mill scale and associated contaminants from the substrate. Common metals and alloys are protected from corrosion principally by painting schemes in applications such as manufacturing, structure protection, and automobile fabrications. Paint life depends on various factors such as the metallic substrate, the selected painting scheme and the paint-substrate interphase. In automobile and manufacturing industries, where plain steel generally is painted, a wash primer coat is typically used to increase the adherence and to improve the anti- corrosive quality of painting films. These primers, known as reaction primers are formulated basically with phosphoric acid (H3PO4) and zinc chromate (ZnCrO4) in alcohol medium, where polyvinyl butyral participates as a ligand of the reaction product.

Evaluating Zn, Al and Al–Zn coatings on carbon steel in a special atmosphere

This paper presents a comparative evaluation of Al, Zn and Al–Zn coatings on carbon steel, exposed to a coastal-marine atmosphere. It is a very aggressive atmosphere with high wind velocities (corrosion–erosion rate ≈ 1.4 mm/year (55.12 mpy) for ASTM 1029 steel). Two flame spraying zinc coatings with pore sealers were also evaluated. ISO and ASTM standards were used for the evaluation. After a 2-year exposure the best performance was achieved by the flame spraying Zn/15Al alloy (85% Zn–15%Al) with some damage of the coatings. But the one with a wash primer pore sealer did not show signs of damage.

Watch your step when working with old paints and wash primer

Type-2-Diabetes (T2D) is the most common metabolic disease in the world today. It erupts as a result of peripheral insulin resistance combined with hyperinsulinemia followed by suppression of insulin secretion from pancreatic β-cells. Mitochondria play a central role in β-cells by sensing glucose and also by mediating the suppression of insulin secretion in T2D. Here, we will summarize the evidence accumulated for the roles of β-cells mitochondria in T2D. We will present an updated view on how mitochondria in β-cells have been associated with T2D, from the genetic, bioenergetic, redox and structural points of view. The emerging picture is that mitochondrial structure and dysfunction directly contribute to β-cell function and in the pathogenesis of T2D.

Non-Chromate Surface Protection for Aircraft Maintenance

While chromates as anti-corrosion pigments in primers and wash primers have disappeared in most industries, there are still quite a lot of chromated paints used in the aircraft industry. Intensive efforts to develop alternative pre-treatments to chromate conversion coatings and to chromic acid anodization have begun. The intention of this report is to give an overview of the state-of-the-art techniques about such pre-treatment/coating systems of aluminium for aircraft maintenance, which are in accordance with the latest environmental policies. The objective is to evaluate the combination of surface pre-treatment and paint as a whole.

Lead in paint; wash primers; and calculating particulate emissions from spraybooths

Lead in paint; wash primers; and calculating particulate emissions from spraybooths

Formulation and testing of a waterborne primer containing chestnut tannin

The development of a water-based pretreatment system containing chestnut tannin and phosphoric acid and the assessment of its anticorrosive properties through different conventional tests are discussed in this work. Treated steel panels coated with different paint systems were subjected to standardized (salt spray, humidity chamber, adhesion, and flexibility) and electrochemical (corrosion potential, EIS) tests. Electrochemical tests were performed by employing only panels coated with the wash primer to determine its protective effect. The binder employed in this research was prepared in the laboratory by emulsion polymerization of acrylic monomers.

Anticorrosive performance of duplex systems on steel surfaces

Galvanized steel specimens were coated with four different organic systems, containing either special acrylic resins or epoxy resins with or without wash primer. The anticorrosive performance of these duplex systems when exposed to an environment of 3.5 percent w/w NaCl solution, was investigated by electrochemical impedance spectroscopy, corrosion potential monitoring, potentiodynamic polarization and dielectric measurements. Interrelation of the obtained results, confirmed by visual observations after salt spray and weathering tests, shows that all four coating systems are more protective than simple galvanizing. The system, comprising a wash primer, a two‐component epoxy resin primer and an epoxy resin finish paint, demonstrates the best anticorrosive behavior among the four systems examined.

Evaluation of the surface treatment effect on the corrosion performance of paint coated carbon steel

Electrochemical impedance spectroscopy studies were carried out for plasticized chlorinated rubber coated carbon steel sheets under free corrosion conditions when exposed to artificial seawater. Four different sample types were used (sandblasted, pickled, pickled+phosphatized and sandblasted+wash primer). Electrochemical impedance spectroscopy (EIS) data was interpreted considering the values of the distinct equivalent electrical circuit models, whose components allowed a quantitative evaluation of the long term corrosion behavior for the different pretreated coated steel specimens. Furthermore, from impedance data, the water content of the paint on the steel substrate was calculated by the Brasher expression and the progress of the coating delamination process was calculated by an empirical expression relating to the measured/specific double layer capacitance ratio. On the basis of both the electrochemical and the visually monitored test results it was concluded that the best corrosion performance was provided by pickled+phosphated painted steel surfaces followed by the pickled surfaces. This result was attributed to the fact that such surface treatments might improve the barrier protection and the steel/paint adhesion properties or reduce the osmotic pressure effect, respectively.

Evaluation of the anticorrosive behaviour of organic coatings applied on galvanised steel surfaces

The study of the anticorrosive behaviour of the four systems of organic coatings — two with coal tar epoxy layer and two with zinc rich epoxy layer and external coating with epoxy paint — which were applied to galvanised steel specimens and were exposed to NaCl solution leads to the following conclusions: ▀ All four systems investigated provide higher protection than simple galvanising during the exposure time of the present work, exhibiting corrosion current densities lower than those of the uncoated galvanised steel even after 4 months of exposure. ▀ The systems comprising coal tar epoxy demonstrate higher anticorrosive protection than the systems with zinc rich epoxy and external coating with epoxy paint. The former maintain lower corrosion curent densities, almost constant phase angle (80°–85°) in the whole frequency range of the measurements, and high values of coating resistance, resistance of pores, and exponent of the CPE of the bulk of the coating. These elements indicate a homogeneous and resistant system with no considerable change of its electrical characteristics which retains its capacitive behaviour, a fact which is also verified by the slight increase in the water uptake(%v) and by the visual observations. On the contrary, the latter demonstrate higher corrosion curent densities, a step-by-step decrease of the phase angle, a significant reduction of the coating resistance, the resistance of pores and the exponent of CPE, and the increase in the constant of CPE, clues which characterize non-homogeneous materials where an increased penetration of polar water molecules occurs. This is also confirmed by the tendency for an increased water uptake, the high values of dielectric losses and the appearance of conductive pathways. ▀ Independent of the coating system, the existence of a wash primer layer leads to an increase of the anticorrosive protection.