Corrosion protection salt spray test

Salt spray test. The model coatings of Table I are of the high solid type used in automotive top coats. Their primary function is not corrosion protection since this is first of all a matter of phosphate layer, electrocoat and/or primer. However, the topcoats may contribute to corrosion protection by their barrier function for water, oxygen and salts. Therefore their permeability is important as one of the factors in the corrosion protection by the total coating system. We feel that a salt spray test of the model coatings directly applied to a steel surface is of little relevance for their corrosion protection performance in a real system. 

Dipping. A process applied to treatment of ammunition and its component metal parts in an effort to protect prevent corrosion of the surfaces. Various chromate dippings (such as Cronak, Irridite, Yellow Black Anodize have been used especially when plating is first applied. The usual requirement of a dipping process is that the 24-hour salt spray test must be met Ref Ohart (1946), 14... 

Two types of corrosion evaluation tests, SO2 and Prohesion salt spray tests, were employed for the evaluation of corrosion protection characteristics of painted plasma systems. The SO2 salt spray test was chosen to speed up differentiation of the corrosion protection properties of the different systems investigated. The Prohesion... 

E-coat stripping. Both plasma-treated panels show excellent corrosion protection performance as compared to the control panels. All [2A] panels with different plasma treatments and plasma polymer coatings, which were corrosion tested in both SO2 and Prohesion salt spray tests, were similarly scanned, and the corrosion width was evaluated by using a scanned image and computer calculation of the corroded area. Figure 31.19 compares the corrosion width obtained by the two methods. 

Figure 31.29 summarizes the corrosion widths along the scribed lines that were calculated from (1) SO2 salt spray-tested and (2) Prohesion salt spray-tested A1 alloy panels and their corresponding control panels. As seen from Fig. 31.29, the corrosion test results showed that the plasma coating systems based on the chromate-free spray primers provided excellent corrosion protection for the A1 alloys studied. 

Figure 32.3 shows the scanned images of SO2 salt spray-tested IVD Al-coated 7075-T6 panels one control, and two E-coated panels. The direct application of E-coat to IVD-coated panels (with no plasma treatment) did not provide corrosion protection as good as that of the chromate conversion oated control panel more corrosion creep from the scribed lines was observed on [7I]/E panels than on the [7pI]CC/E... 

The corrosion widths of Prohesion salt spray-tested IVD Al-coated Al panels were calculated and are summarized in Figure 32.6. As is evident from the data, after 12 weeks of Prohesion salt spray testing, IVD/plasma polymer/spray paint systems showed better corrosion protection overall than IVD/plasma polymer/E-coat systems. All the IVD/plasma polymer/spray paint systems outperformed the cathodic E-coated controls and showed corrosion test results comparable to those of the Deft primer oated controls. 

The corrosion widths of Prohesion salt spray-tested alloys are calculated and summarized in Figure 32.14. E-coated IVD controls (CC/E), i.e., the combination coating systems of chromate conversion coating with nonchromated E-coat, showed very large corrosion widths for all the IVD Al-coated aluminum alloys. This combination did not provide good corrosion protection, which could be taken as proof that the two completely different approaches (electrochemical corrosion protection and corrosion protection by barrier adhesion principle) should not be mixed. 

Figure 32.22 shows the comparison of average corrosion widths from both (a) SO2 salt spray-tested and (b) Prohesion salt spray-tested IVD panels. Both SO2 and Prohesion test results show that chromate-free LCVD coating systems provided excellent corrosion protection on IVD Al-coated A1 alloys, having comparable or... 

Uncertainty of mass loss measurement. The standard method of the neutral salt spray test does not indicate the mass of RS. Mass loss was found as a difference between the RS prepared for the corrosion test and the RS after the corrosion test and corrosion product stripping as well as protective coating removal from the RS (Table 1). Such a mass loss determination is based on three components (1) mass loss determination by weighing (accuracy 0.5 mg and standard deviation 0.3 mg) before the neutral salt spray test and after it, (2) determination of difference and (3) cor-... 

Yellow chromating The bath contains 2 to 20 g 1 chromium as chromic acid or dichromate, 1 to 5 g 1 sulfuric acid, and 0.1 to 1 g 1 sulfate, chloride or nitrate as a catalyst for the chromate reduction. The film has a yellowish color and a thickness of up to 1 (xm. This film is very efficient in corrosion protection, and a time of500 h in a salt spray testing without any corrosion spots is achieved. Moreover, the film has the property of self-healing of mechanical defects, which makes this procedure so superior to alternatives. But the film contains up to 200 mg m chromate and this will probably soon lead to an end of this very cheap and effective protection process. 

Salt spray test was carried out as per standard [21] using CMEIPL, India as shown in Fig. 2.9 to find out corrosion rate of uncoated panel and the degrees of protection afforded by coated panels. Panels were exposed to 5 % NaCl solution sprayed with compressed air at 6-8 bars and the fog generated inside at 35 °C was... 

In salt spray test, the corrosion rate was again higher for MS but the difference with WS was not much. Perhaps this was due to continuous formation of non-protective mst in NaCl on both MS and WS. 

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